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HARI SREENIVASAN: A bipartisan group of senators today introduced a sweeping immigration reform bill, after months of negotiations.

But in the wake of the Boston bombings, they delayed a public announcement until later this week. The legislation is designed to put some 11 million people on a path to U.S. citizenship and to invest billions of dollars in strengthening border security. It also includes a new farmworker program and visas for high-tech workers.

American Airlines was forced to ground its entire fleet for much of the afternoon after its reservation system went down. The grounding triggered major travel delays that rippled throughout the country and abroad. Many passengers, like those at American's main hub in Dallas/Fort Worth, were stuck on planes. Other customers were unable to make or change their reservations. American operates more than 3,500 flights worldwide every day.

A showdown may be looming in Venezuela, after a disputed presidential election. President-elect Nicolas Maduro warned today he will not allow an opposition march tomorrow. He blamed protesters for Monday's clashes that killed at least seven people and injured dozens in Caracas and other cities. The demonstrators demanded a full vote recount, something elections authorities have ruled out.

Maduro charged today it's all part of a coup plot orchestrated by opposition candidate Henrique Capriles.

PRESIDENT-ELECT NICOLAS MADURO, Venezuela: The results were impeccable. They know it, the group that has ambitions of excessive power, that has so much hate within, and that yesterday went crazy calling for violence from the people in the street. I can announce here we have defeated a coup, but they are going to continue to destabilize. Today, I declare the coup defeated.

HARI SREENIVASAN: The official results from Sunday's election showed Maduro winning by 265,000 votes. Opposition officials say their count shows that Capriles won by more than 300,000 votes.

A major earthquake struck southeastern Iran today, killing dozens of people. The quake registered a magnitude of 7.7 and was centered near Saravan, about 26 miles from the Pakistani border. It flattened homes and killed at least 34 people on the Pakistani side. In Iran, state media initially reported at least 46 killed, but later dropped any reference to deaths.

In economic news, U.S. homebuilders started work on more than a million units in March, the most in nearly five years. And on Wall Street today, stocks made up a big chunk of yesterday's losses. The Dow Jones industrial average gained more than 157 points to close well above 14,756. The Nasdaq rose 48 points to close at 3,264.

Long time NFL broadcaster Pat Summerall died today in Dallas. He had been hospitalized after breaking a hip. Summerall played 10 seasons in the NFL and then worked as a broadcaster for more than 40 years. For 21 of those years, he called NFL games with John Madden. Overall, he worked 16 Super Bowls, 27 Masters golf tournaments, and 21 U.S. Open tennis championships. He retired in 2002. Pat Summerall was 82 years old.

Those are some of the day's major stories -- now back to Gwen.

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GWEN IFILL: We return again to the bombings in Boston.

To help us assess what we know about the attack and explain what investigators are looking for now, we turn to Juan Zarate, who was deputy national security adviser for terrorism under President George W. Bush, and is now at the Center for Strategic and International Studies, and Don Borelli, a 25-year FBI veteran who is now chief operating officer of he Soufan Group, which consults on security matters.

Juan Zarate, the president said today the investigation is in infancy, but from what we know, we now know that there was a pressure cooker involved, that there may have been beads involved or BBs involved, shrapnel in any case, and that maybe a circuit board was found that was used as a timer.

What does this tell us about the source of this explosion?

JUAN ZARATE, Center for Strategic and International Studies: Well, Gwen, this is part of the forensic work that happens now.

And what authorities are looking for are signatures in the devices themselves that can give them some clues as to who may have been behind the attacks. What this tells us, at least to date, what we know is this was designed to have maximum effect, even though the explosive charge itself wasn't massive.

It was designed with the ball bearings and the nails and other shrapnel to have maximum impact upon explosion. And so what that tells us is that this is more than the work of sort of a mere amateur, but it's certainly not sophisticated enough to tell us that it's the work of a bomb-making mastermind.

And so this, again, is helpful, it's probative, but it doesn't give authorities enough to determine if we're talking about a lone wolf actor or a downsized al-Qaida-inspired attack.

GWEN IFILL: Don Borelli, how do you read that? You were on the New York City joint terrorism task force. And we now know that there are maybe 2,000 -- 2,000 tips or more coming into the Boston Police Department and the FBI. Is that helpful? Is that just a lot to get through?

DON BORELLI, The Soufan Group: It's both.

We have seen in context of the medical teams talking about the word triage, where they had to triage the wounded individuals. This is the theory going on now with the FBI. They're getting thousands of leads from citizens, from informants, from our partners overseas, from everywhere.

And they have got to prioritize those leads and triage them and work the most positive ones first and the ones that are potentially perishable.

GWEN IFILL: We have been watching, Juan Zarate, the investigators literally combing the streets where the bombing occurred on their hands and knees, picking up every little thing.

If it rains tonight, as the reporter from the WBUR was saying, does that impede the investigation?

JUAN ZARATE: It will a bit.

The crime scene is outside. The wind and the rain and the elements no doubt will have an impact. And so the FBI investigators, the federal authorities, state and locals, who are part of this, are no doubt doing everything possible to gather bits of information and detritus on the ground before the rains hit.

But, in addition, as we have heard, they're talking to witnesses. They're trying to crowd-source evidence gathering. They're looking -- the intelligence community is looking back at intel. We have heard, for example, Gwen, that there was no chatter before the event.

But keep in mind that, before the underwear bomber, Abdulmutallab, who tried to explode the underwear bomb over Detroit, there was also at least initially a sense that there wasn't chatter before. But, upon retrospect, there were bits and pieces of intelligence data that had not been put together. And so it's forensic work on the ground, but also intelligence work, both retrospectively and prospectively.

GWEN IFILL: Don Borelli, we obviously don't have enough information to get into too much speculation here, but based on your experience with investigating these types of crimes, is there any -- are there any signs here that this is domestically, a homegrown kind of activity, or this something that would only be done by al-Qaida or someone else who would usually claim responsibility?

DON BORELLI: It's in -- in my opinion, it's way too early to tell.

There are some things that would lend me to think that it's maybe more homegrown just because of the type of devices used. As Mr. Zarate said, these weren't overly sophisticated devices. They were effective, but not the type of things that we have seen when individuals travel to Pakistan, Afghanistan and get the training.

For example, you compare it to the attempted New York City subway plot in 2009 with Najibullah Zazi, where he was actually going to use TATP, which he had learned to make overseas. So there -- certainly, that was a bit more -- it took more training, more complicated, and had that international aspect to it, whereas this -- as we have seen and heard, you can get the recipe for this -- these bombs, these pressure cooker bombs, on the Internet anywhere.

GWEN IFILL: Juan Zarate, you worked in the White House. Is it significant that the president today chose to use the word terrorism and terror, when he didn't yesterday?

JUAN ZARATE: Well, I think it has political significance.

Keep in mind that the U.S. government has a definition under criminal law and otherwise for what terrorism is. And I think initially the president wanted to be very careful not to be the first fact witness as to what was happening, not committing to any set of facts or criteria.

But I think obviously seeing what had happened, understanding what the FBI was starting to see, understanding the nature of these explosive devices, that he was comfortable and probably felt a little bit of political pressure to call it what it is, which is an act of terror.

I think the real trick here is the White House wanting to calibrate the judgment, not wanting to jump to conclusions, and also wanting to send a message of national resilience, which is something you have heard consistently not just from the White House, but from homeland and counterterrorism officials for the last couple of years.

GWEN IFILL: Don Borelli, as the nation struggles to try to find the balance between that kind of resiliency and yet awareness of what might be going on, does it matter that this is a different kind of venue, that is to say, a big spectator event, where someone knew there was going to be a lot of attention paid?

DON BORELLI: Well, there's -- you know, it's a double-edged sword.

The fact that there are so many spectators, so many cameras, that gives the investigative team that many more leads, because, as we have heard, there's been so much assistance from the citizens of -- sending in their films, their stills, the video cameras.

On the other hand, we always look at these major events as an opportunity for a terrorist to strike. So whether it's the Super Bowl, the marathon, New York New Year's Eve, when you have a lot of people in one space and a lot of media coverage, this is a recipe for a terrorist attack, should they want to take advantage of it, because not only you can inflict damage on a lot of people, but with the eyes of the world watching, you can really have that psychological impact as well.

GWEN IFILL: Let me ask you to follow up on that, because with the eyes of the world watching, the officials in Boston have made a repeated attempt to get people to say -- to give up their pictures, their videos, their cell phone photos.

How -- is that what they have to rely on now to break this case? Is that why they're making that public appeal?

DON BORELLI: I think they're not relying on any one investigative technique, but they're exploring all options.

They're going to be using photographs. They're going to be using eyewitness statements, informants, technical information, maybe cell phone, what was going on in the cell phone towers before and after the bombings.

So, you know, it's not just the pictures, that's a piece of it. But you have to look at every avenue that could give you potential information to go out and pursue further leads.

GWEN IFILL: So, Juan Zarate, we're no longer depending on claims of responsibility by shadowy figures anymore?

JUAN ZARATE: That's right.

I think the fact that you don't have claims, you don't have a signature to the nature of the strike itself makes it altogether more difficult to determine responsibility and to attribute the attack.

And I think, unfortunately, that's the world we live in, in terms of terrorism. It could be terrorists of any ideological stripe. It could be a lone wolf actor. It could be a network set of actors. And I think that's, unfortunately, the world we live in.

GWEN IFILL: Is it fair to say we have to be prepared for this investigation to continue for some time?

JUAN ZARATE: I think that's right.

I think we need to look back, for example, to the 1990s, where you had domestic terrorist attacks that took a long time to actually figure out. Remember the manhunt for Eric Rudolph, the Centennial bomber, something similar to this attack. Keep in mind, the Unabomber; it took a while to figure out who was behind it.

I think we have grown accustomed to the al-Qaida-style attacks, where they claim responsibility, where there are signatures to it, fairly easy to attribute, where the responsibility and attribution is actually part of the political program and messaging from the terrorist group.

This may be a case where the people who perpetrated it don't want to be found. And that will prove difficult for the investigation.

GWEN IFILL: Juan Zarate and Don Borelli, thank you both so much.

JUAN ZARATE: Thank you.

DON BORELLI: Thank you. 

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JEFFREY BROWN: Now a firsthand account of the emergency medicine administered to victims and the challenges they will be facing.

Patients were sent to seven hospitals across Boston yesterday, including Massachusetts General.

Dr. Alasdair Conn heads the hospital's department of emergency medicine.

Hari spoke with him a short time ago.

HARI SREENIVASAN: Dr. Conn, thanks so much for joining us.

What can you tell us? What is the latest on the status of the patients that you have?

DR. ALASDAIR CONN, Massachusetts General Hospital: We have 12 patients that were admitted to the hospital yesterday following this explosion.

Last night, we listed eight as critical, and we're now listing seven as critical, although we're hoping that one will improve overnight, so that will leave us with six. Four of the patients, unfortunately, had an amputation of one of their lower extremities.

HARI SREENIVASAN: Now, what types of injuries are you seeing? We have heard so much about these lower extremities. In fact, one of your colleagues this morning said that you're completing the job that the bomb began.

ALASDAIR CONN: That's correct.

They were -- when they arrived, they were virtually complete amputations. And it was very obvious in the emergency department and subsequently in the operating room that there was so much damage that these could not be reattached, if you like.

And so basically we were completing what the explosion had already done. The other injuries did require -- there seemed to be a lot of metal fragments from the explosive device. And these caused a lot of damage to the musculature, and particularly in one patient to the blood vessels supplying the lower extremity.

We did have one of the vascular surgeons repair the blood vessels, so we're hopeful that we will be able to salvage that limb. It's still a little bit of early days, though.

HARI SREENIVASAN: So, what happens to some of that shrapnel? Is it going into the hands of federal investigators trying to piece together ...

ALASDAIR CONN: Absolutely.

Any material that is going to help in this investigation was handed from the operating room to the appropriate authorities for them to obviously see what they can determine about the people who led to this tragedy.

HARI SREENIVASAN: And when you say metal objects, what does that mean? Are these sharp like nails? Are they round like BBs? What was in there?

ALASDAIR CONN: The one thing that impressed me first looking at the C.T. scans and the X-rays as soon as we had them developed was the number of small, like BBs that were in the wounds, not only the lower extremities, but in some patients elsewhere on the body.

And Dr. Velmahos, who did a lot of the surgery, was saying that some of the metal objects appeared to be like nails that, that the head had been cut off in some way. So, again, all of these were collected when we removed them from the patients and give them to the authorities from the operating room.

HARI SREENIVASAN: Now, you're the chief of the department of emergency medicine. You train for something like this, but how different is it when this comes through your door?

ALASDAIR CONN: We train for it.

We're very fortunate in Boston. We have gone through a lot of disaster drills. But this was the real thing. We certainly see horrific injuries, but it's usually one patient at a time, and, yesterday, 12 patients in the course of less than an hour.

Fortunately, we were able to mobilize the resources. And within just a few minutes, we had five patients from the emergency department right up to the operating room. And those were obviously the most critical patients.

HARI SREENIVASAN: And so what's next for these critical patients? What are you looking for and watching out for in the next 24-48 hours?

ALASDAIR CONN: What we do in the first operation is obviously salvage as much viable tissue as we can. The patients will be taken back to the operating room almost on a daily basis, and we will be cleaning out the wounds, eventually doing some tissue transfers to cover the wounds, skin grafts in other patients, and waiting until we can get complete coverage of the wounds.

We're hopeful that the -- no more patients will lose a lower extremity. That's what we're hoping for -- and that the people who have lost their lower extremity ultimately will be able to be fitted with a prosthetic limb.

I will say, one of the orthopedic surgeons here has received calls from patients who he's previously operated on calling up and saying, look, I have been living with my artificial leg. I have a full life. I can walk. I can run. I can jog. I would love to come in when the time is right and help people initiate their rehabilitation process.

HARI SREENIVASAN: I know you had sent some of your patients across for ear damage. Was that from the explosion?

ALASDAIR CONN: Yes, it was.

A blast injury, if they're very close to the explosion, it can literally rupture the eardrum. And those patients, we sent across to the Massachusetts Eye and Ear Infirmary to have their ears more appropriately managed.

HARI SREENIVASAN: Are there dangers of concussion wounds for all of these patients, too?

ALASDAIR CONN: They were in danger, but after evaluation here, we felt comfortable that they didn't have any severe concussion and that we wanted to get them examined to determine if there was any damage to their tympanic membranes and their hearing.

HARI SREENIVASAN: And what about things like blood pressure, considering the loss of blood and limbs and so forth? How do you regulate that?

ALASDAIR CONN: Well, certainly, one of the things that is gratifying was the way that EMS and all of the personnel on the scene brought the very severely injured patients to our emergency department and to other level one trauma centers within the city in a very fast manner.

One or two patients had very low blood pressure when they arrived. We gave them blood in the emergency department to bring up their blood pressure and then sent them immediately upstairs. And obviously the treatment is to stop the bleeding, control the hemorrhage, and then give them blood transfusions to bring their blood pressure up and normalize.

HARI SREENIVASAN: Dr. Conn, in an odd way, a doctor I spoke to yesterday says it couldn't have happened in a better location. There was almost an entire medical hospital there at the finish line.

ALASDAIR CONN: That's correct.

We had -- we have -- some of our physicians and nurses were manning some of the medical tents along the way. And, obviously, as these -- this explosion occurred, things took a rather more serious turn. One of our trauma surgeons, an actual fact, ran the marathon and, when he finished, realized what was happening and came in to operate on some of the patients.

HARI SREENIVASAN: Wow.

Dr. Alasdair Conn, thanks so much for your time.

ALASDAIR CONN: Thank you.

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GWEN IFILL: Technology changed the speed and the accuracy with which we learned of the Boston attacks, but it also quickly became a platform for the nation's shock and grief.

NewsHour political editor Christina Bellantoni talked with our Daily Download team about that.

CHRISTINA BELLANTONI: For that look at how technology factored into yesterday's tragedy I'm joined by Lauren Ashburn, Daily Download editor-in-chief, and Howard Kurtz, Newsweek's Washington bureau chief and host of CNN's "Reliable Sources."

Thanks for being here.

So, after 9/11, we saw people physically putting up photos of their missing loved ones in Lower Manhattan. Yesterday, the Internet provided a sense of comfort for some. What did we see?

LAUREN ASHBURN, Daily-Download.com: Well, Google Person Finder factored into this. We have a graph that can show you exactly what it looks like.

There's a big button that says "I'm looking for." You can type in the name of somebody. Or "I have information about," and you can also type in the name of someone. Then you can take this tool and embed it on your own website.

So, in the aftermath of disaster, Howie, it really seems like this tool and others are much more effective than going to the bulletin board near the World Trade towers and scanning all of the pictures.

HOWARD KURTZ, Newsweek/CNN: And the tone of Twitter, where there were about five million tweets in 24 hours according to the website Topsy, was very striking to me, because, in the beginning, when Twitter was young, journalists kind of looked down their nose, well, anybody can post anything. How do we know it's true? And often things were not true.

Now, while there were examples of excesses in partisanship, I found, really, Twitter has almost grown up. There was a tone of restraint and people saying they were not going to retweet every last bit of speculation, and even criticizing the mainstream media for speculating about who was behind this attack.

LAUREN ASHBURN: Journalists did that, too.

CHRISTINA BELLANTONI: And there was a lot of misinformation about there. You have seen that in the wake of a lot of different types of tragedies, that major news ...

LAUREN ASHBURN: Not so much now, though, during this one.

You remember Hurricane Sandy, when there were doctored pictures of a shark swimming through a New Jersey neighborhood. And the call, as Howie said here, was for restraint, a lot of journalists and other people saying don't retweet things that you don't know to be true.

HOWARD KURTZ: There was the New York Post mistakenly reporting, for example, that the death toll was 12, not initially two or three, and saying there was a Saudi suspect, when that was unconfirmed. Twitter spanked the news organizations that went off the rails.

CHRISTINA BELLANTONI: Sure.

And, on Facebook, this became a site where people could check in on their friends that were running the marathon or people that lived up there. You also saw like this online tribute that was created by a D.C.-based designer, Matt Ortega. He posted all these sports-themed Facebook images that you could share with your friends to sort of show solidarity there.

LAUREN ASHBURN: I saw lots of memes put together, a heart of the city of Boston saying "We love you" that had the actual map of the city on it.

It was an outpouring of love, as there is oftentimes amidst tragedy. But there was also not some very helpful things. There was an "_bostonmarathon" on Twitter that was taken down within an hour because it was fake. They were asking for money. And we have seen that a lot in the past. But this one was caught very quickly.

HOWARD KURTZ: And not just on Facebook, but as you were saying before we came on the air, on Tumblr and Instagram. You had a sense of community, sharing of photos, sharing of feelings, sharing of sympathy.

It used to be television was the place where everybody gathered around the hearth. And television still played a very important role, the broadcast networks going wall-to-wall for a while, but now you see that much more online. And the tone was heartening.

CHRISTINA BELLANTONI: Even our own Mr. Rogers from PBS, this quote that he said about finding the helpers, that's a way to comfort children in times of tragedy, was going viral.

LAUREN ASHBURN: I found it very interesting also who was first.

You know, journalism, part of the problem in breaking news stories is that everybody rushes to be first. Well, here, it was a Twitter picture of someone saying "Holy cow" and hashtag "explosion." And that was at 2:50 p.m. on Monday.

HOWARD KURTZ: Monday.

LAUREN ASHBURN: And then the Boston Police Department didn't confirm it until 3:39.

Twitter had the actual pictures and eyewitness accounts, and TV and radio and the Net had to really play catch-up.

HOWARD KURTZ: There are more people tweeting than there are journalists in the world. So, it's often going to get there first.

CHRISTINA BELLANTONI: Sure.

And you saw some actual physical tributes, like this Light Brigade picture that we have here, the Overpass Light Brigade. This was something that was really shared a lot on social media as well.

LAUREN ASHBURN: And there were other ones, too, like that, in different cities. There was one in New York that said "N.Y. Heart" and then a B. in the ...

HOWARD KURTZ: Boston Red Sox, yes, logo.

LAUREN ASHBURN: ... Boston Red Sox logo.

HOWARD KURTZ: You mentioned the Boston Police Department. Now, that was very aggressive in using online, Twitter.

CHRISTINA BELLANTONI: Yes.

Let's talk more about how investigators are soliciting this information from crowds via social networking, like this tweet from the Boston Police Department saying that we're looking for video of the finish line. Is this unusual?

LAUREN ASHBURN: Well, they used it more.

What I found interesting is if you looked at the Boston Police Department's Twitter feed, at 1:38 in the afternoon, they put up a picture of runners at the finish line. And at -- by the time it was 3:39, they came out with the announcement. They used that Twitter feed to get out information, like a -- commissioner, what he's saying, what areas are closed, what you can do for loved ones, where you can find things.

And the Massachusetts Emergency Management Agency said, use your -- if you're having a problem with your cell phone, use your texting, and that has less bandwidth.

HOWARD KURTZ: With cell service having been shut down for a while after the bombings, this really was the way to communicate for the police and for people using social media.

CHRISTINA BELLANTONI: Lauren Ashburn, Howie Kurtz, thanks very much.

HOWARD KURTZ: Thank you.

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GWEN IFILL: Tribal law, federal law, and the fate of a young girl. The Supreme Court heard a rare child custody case today.

Ray Suarez has that.

RAY SUAREZ: The little girl at the center of this case is known as Baby Veronica. She's caught in a custody battle, the kind normally heard in local courts. But the case was heard today by high court justices since it raises larger questions about federal law because the girl is part Cherokee Indian.

The Indian Child Welfare Act was passed in 1978 to protect children and the stability of Indian tribes. It allows tribal involvement in custody decisions, so Indian children aren't unnecessarily removed from their ethnic origins.

Marcia Coyle of the National Law Journal was in the courtroom this morning, and is back with us tonight.

And, Marcia, when people hear custody battle, they tend to think mother vs. father, but this was kind of a three- or even four-way legal argument, wasn't it?

MARCIA COYLE, National Law Journal: Absolutely, Ray.

You had the lawyer for the adoptive couple here who had custody of the child for about 27 months. You had the lawyer for the guardian ad litem for the child. And then on the other side, you had a lawyer for the biological father of the child and a lawyer for the United States arguing.

RAY SUAREZ: So why was the Indian Welfare Act -- Child Welfare Act passed in the first place, and does the biological father clearly fall under its provisions?

MARCIA COYLE: The act was passed in response to a real crisis.

It's estimated that roughly 35 percent of Indian children were being removed from Indian families by abusive child welfare agencies and being placed in -- either in adoptive homes or in foster care and generally non-Indian foster care or adoptive homes.

So Congress responded to that with this act, which does provide special protections for Indian families, as well as for Indian tribes.

RAY SUAREZ: Was there any argument over what makes someone an Indian?

MARCIA COYLE: There really wasn't specific argument about that, but there were questions raised, some skepticism about how much of an Indian this child is.

Chief Justice Roberts, Justice Alito raised questions about, well, this child is three-and-256ths of Cherokee blood. What if you had a tribe, for example, that decided that it would allow anyone to enroll who didn't have any Cherokee blood, and someone did enroll like that, had a child; would that child then be considered an Indian child?

They posed several hypotheticals trying to get at how far the act really reaches. But, as the lawyer for the biological father explained, there are federal requirements for recognition of tribes, and those hypotheticals are rather extreme. But, also ...

RAY SUAREZ: But this is an issue in this case, isn't it, because it's the father's status as an Indian which he's arguing trumps other kinds of claims and other findings in state courts, which normally handle custody battles.

MARCIA COYLE: That's right.

And there are no blood tests under this act. He -- because he is the biological father, he does fall under the definition of an Indian parent. But the parties do dispute how the act applies in the situation where they claim -- at least the adoptive couple claims that the biological father here, he was an unwed father. There's an exclusion under the act for parents, unwed fathers who do not assert or establish paternity.

The dispute is that the biological father says that he did do that as soon as he was made aware of the adoption proceedings. The adoptive couple's attorney claims too little, too late.

RAY SUAREZ: The non-Indian couple, the Capobiancos from South Carolina ...

MARCIA COYLE: Yes.

RAY SUAREZ: ... who adopted the little girl, it appeared from the transcript as if some of the justices weren't altogether comfortable with having to make a call in this case.

MARCIA COYLE: I think there really was some discomfort.

Justice Kennedy at one point pointed out that federal -- I'm sorry -- state courts, family courts deal with these kinds of problems all the time. And he said the first family judge really was King Solomon, and if they could appoint King Solomon as a special master here, they would, but they can't.

So it clearly is posing some difficult issues for them. There seemed to be almost a divide on the court between justices who felt that the language of the law is quite clear, that the father is a parent under the law, and that special protections kick in because he is an Indian parent and this is an Indian child, and other justices concerned about whether the best interests of the child were -- are really considered in this situation. Does state law apply at all in making the decision as to who should have custody?

So, yes, I would say that they're uncomfortable with this.

RAY SUAREZ: There were separate arguments from the lawyers for the adoptive couple ...

MARCIA COYLE: Right.

RAY SUAREZ: ... for the biological father, Dusten Brown, and for the guardian appointed by the South Carolina state government.

MARCIA COYLE: Right.

RAY SUAREZ: What were the central conflicts from these three separate views of the law?

MARCIA COYLE: Well, on the adoptive parents' side -- and they are supported by the guardian ad litem in this case -- they argue that, even if the father -- even if the father is a parent under the law, he has no legal rights. He had no relationship with this child, that the Indian Child Welfare Act presumes an existing Indian family. It's all geared to preserving an Indian family, and there was no family here.

On the other side, the father and the United States argue that the father does fit the definition of parent, and the South Carolina Supreme Court, as well as the state family court, applied the federal law accurately in refusing to terminate his parental rights. They found that he would provide a loving home and family for the child and met the other requirements of the law.

RAY SUAREZ: The Obama administration and many Indian tribes came in on the side of the biological father. We will find out how it all turns out later in the term.

Marcia Coyle, thanks a lot.

MARCIA COYLE: My pleasure, Ray. 

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JEFFREY BROWN: It is indisputable that the United States engaged in the practice of torture after 9/11. That was the starkest finding in a report released today by the Constitution Project, a bipartisan legal research and advocacy group, after a two-year investigation by a task force of former high-ranking government, military, and law enforcement officials.

Among much else, the report concludes that the nation's highest officials bear some responsibility for allowing and contributing to the spread of torture, and that information gleaned via harsh interrogation yielded little valuable intelligence. The report also criticizes the Obama administration for what it calls excessive secrecy.

Two members of the task force that produced the report join us now. James Jones, a former Democratic congressman and ambassador to Mexico, co-chaired the group, along with Republican Asa Hutchinson. Also with us is David Irvine, a retired Army Brigadier General and former Republican state legislator.

And welcome to both of you.

FORMER CONGRESSMAN JAMES JONES, D-Okla.: Thank you.

RET. BRIG. GEN. DAVID IRVINE, U.S. Army: Thank you.

JEFFREY BROWN: Jim Jones, indisputable that the United States practiced torture.

At the time, the Justice Department said otherwise, that within very strict rules, this wasn't torture. What made you say this was?

JAMES JONES: Well, an exhaustive study of the laws of court cases, of the practice, of interviews and all -- the summary of all of it was it was indisputable there was torture in many cases.

JEFFREY BROWN: You were -- just to be clear, you were -- you didn't have subpoena power here.

JAMES JONES: Right.

JEFFREY BROWN: And so how were you doing it? You said by talking to people?

JAMES JONES: Well, the staff and some of the panel members visited several countries, visited the black sites where some of these were, in Poland, Lithuania, et cetera. They talked to officials. They talked to detainees themselves, and they did an exhaustive research of the law.

And the United States has even brought prosecutions for the very same things that we did in some of those sites.

JEFFREY BROWN: David Irvine, former U.S. Ambassador John Bolton told the AP when the report came out that this report is -- quote -- "completely divorced from reality." The procedures were, in his words, "lawyered and lawyered again and lawyered again."

DAVID IRVINE: I think if anyone takes time to read the report, they will be overwhelmed by the volume of episodes where representatives of our government, our military brutally, brutally tortured many, many people, not just people who were among the worst of the worst, as they had been characterized, but often people who were guilty of nothing more than being in the wrong place at the wrong time.

The claim that this was lawyered to death is an interesting claim, because we have had years and years and decades of experience successfully interrogating prisoners in tactical and strategic interrogations. We have never had to rely on this kind of approach to get the information that we needed to get to protect the country.

JEFFREY BROWN: Well, speaking of the information -- well, I'm sorry. Go ahead.

JAMES JONES: Well, I was just going to say the lawyering part is one of the criticisms we have.

In past wars, they say that the generals ran the war. The lawyers ran this war to a great extent. And the way -- by suspending the Geneva Conventions, which we have adhered to for years, by violating the Convention Against Torture, which President Reagan himself proposed and the Congress passed, and the lawyers tinkering with that in such a way that they didn't replace it with anything, and so the chain of command, the procedures that would have been in place were basically obliterated because of lawyering.

JEFFREY BROWN: Now, a much-debated issue has been one what kind of information came from these practices. You say in the report that some former senior officials insist that the techniques did yield valuable information. You conclude otherwise.

DAVID IRVINE: We studied as careful as -- carefully as we could from the public record those specific claims.

The problem we had as we looked at those was that the timelines don't match up. We could not account for the differences, sometimes a matter of days, weeks, even many months, between the critical events of arrest, interrogation, claims of successful gathering of information, and breakup of plots.

There's no synchronicity to that that justifies the claim that thousands of lives were saved as a consequence of brutal interrogation.

JAMES JONES: Let me just add to that, because we -- the -- some of the top officials that say that this torture produced effective information, they have the burden of proof. They can't -- we can't just take their word for it.

We tried to interview several of those, and they refused to be interviewed. So one of the reasons we're calling for declassifying some of this material is that will say yes or no, it was effective or yes or no there wasn't torture.

JEFFREY BROWN: And you are critical of the Obama administration in that regard for not declassifying, not pursuing a lot of these things.

JAMES JONES: Right. And we hope they will. We hope they will change their mind.

JEFFREY BROWN: Were you able to talk to any top officials in -- among the many people you talked to find out what happened, and, after the fact, after you produced the report, any top Bush era officials about this?

JAMES JONES: We -- of course, we just released it today, and I haven't talked to any of the former Bush administration people.

Obviously, Asa Hutchinson was in the Bush administration, and so this was a tough thing for him to go through. But we came to the unanimous opinion, as reflected in that report.

We did talk to some. The -- David -- Rizzo was the general counsel of the CIA. He gave an interview. And we had some others in the military that we talked to.

JEFFREY BROWN: But when you say in the report that the nation's highest officials bear some responsibility for allowing and contributing to the spread of torture, what does that mean? What exactly are you calling for?

DAVID IRVINE: Well, in a couple of instances, number one, the decision to suspend the application of the Geneva Conventions in Afghanistan was a critical decision that opened the door for all kinds of abuses, because there was nothing put in place thereafter that would tell soldiers, for example, what they could or could not do.

As a consequence, people became unusually creative and crossed the line from lawful to unlawful. The decision to give special permission to the CIA to use enhanced interrogation techniques was a flawed decision. It was based upon a methodology that had been developed by the North Koreans and Chinese in the Korean War as a means of obtaining confessions and false information from American prisoners in those conflicts.

JEFFREY BROWN: Let me just ask you briefly in the short amount of time here, what do you want to happen now? You have waded into some very controversial territory here.

JAMES JONES: Yes.

JEFFREY BROWN: And many officials would simply flat-out disagree with your results.

JAMES JONES: Well, we're not after a witch-hunt, but we do think the facts need to be laid out there, the American people need to understand it, the Congress needs to understand it, because what we want to do is to get back to the values that we had before those decisions were made, respect for law, respect for our international treaties and conventions.

And it can be achieved again. But I think until -- before that can be done, they have to understand the depth of the activities we took in the name of our government.

JEFFREY BROWN: James Jones, David Irvine, thank you both very much.

JAMES JONES: Thank you. 

Investigators study the scene on Boylston Street at the site of the second bomb explosion. Photo by John Tlumacki/The Boston Globe via Getty Images.

A day after two blasts rocked the Boston Marathon finish line, investigators are scrambling to unearth clues on the devices and who planted them.

Some early details began emerging on Tuesday. The bombs seemed to have been fashioned out of kitchen pressure cookers, the Associated Press reported on Tuesday, citing investigators. They were likely packed with nails and other shrapnel, some of which has been found embedded in the bodies of the injured. Evidence of kitchen timers were also found.

Some reports said the bombs could have been hidden in a trash can, turning the trash cans themselves into weapons during the explosion. More recent reports suggested they were packed in backpacks or duffel bags and left on the street near the finish line.

"I would speculate that it's some sort of a timed device," said Frank Doyle, a former FBI intelligence analyst who was involved in the investigations of the Oklahoma City and New York World Trade Center bombings. "I would have even gone as far to say that both of these devices attempted to be set off at the same time."

All of these elements will help investigators build what's known as a "signature" of the perpetrator. That will help them hone in on who built this, where they were trained and where they got the materials, said A.J. Clark, a former military intelligence analyst, who says the device appeared to have been designed to create maximum damage to a large crowd.

In the immediate aftermath, investigators will search for remnants of the bomb -- duct tape, for example, or any signs of explosive material. They'll study indentations in the ground -- which will give clues to how closely it was positioned to the road, buildings, a park bench or a trash can.

They'll study videos and still photos captured by witnesses. These videos, Clark said, can prove "tremendously helpful." Already, the white smoke in the videos indicates that the bomb was a homemade device, not military ammunition, dynamite or a C4 explosive, he said. Military explosives of that sort would produce darker smoke.

"It's the chemical makeup," Clark said. "You'll find that stronger explosives have a denser, more explosive power, and they're of a darker nature. Homemade chemicals give off a lighter smoke when detonated."

Then they'll start digging deeper into what's known as biometric forensics. That involves looking for DNA, for example, or fingerprints -- a thumbprint on a sticky part of duct tape, anything available to analyze the type of explosive material used.

"This isn't anything too eloquent," Clark said. " Putting something inside a pressure cooker doesn't add that much complexity to it." Bombs designed using pressure cookers, he added, are commonly found in India, Pakistan and Afghanistan.

But Doyle disagrees with those calling it a "crude" bomb.

"It wasn't crude because it functioned, it worked, it killed people, it obtained a goal," he said. "It was complex enough to kill people, to do what bad people wanted to do."

Eventually, all evidence will be taken to an FBI laboratory, where it will be closely analyzed, Doyle said. They'll comb through swabbings and residues and they'll methodically lay out components, comparing the two explosives and comparing elements thought to have come from the containers with material outside. All of information will be entered into a database to be used in future incidents. Meanwhile, investigators will likely pore through details on other bombings in search of useful patterns.

The 1996 explosion during the summer Olympics in Atlanta's Centennial Olympic Park may provide the best model for Monday's event, said Michael Greenberger, director of the University of Maryland's Center for Health and Homeland Security.

"It's a similar kind of episode," he said. "A bomb that randomly went off with crowds of people around." But, he added, with cell phone videos and other technology, forensics are better now.

In the case of the Atlanta attack, serial bomber Eric Rudolph wasn't arrested until nine years later.

Greenberger said he's optimistic that they'll find the perpetrator of the Boston marathon bombings eventually, but possibly not until evidence is painstakingly pored through and analyzed.

"I have the unfortunate suspicion that this won't be solved quickly," he said.

Related

Photo Gallery: From Triumph to Tragedy

Doctor on the Scene: 'Tons of Mangled Extremities on the Ground'

Teacher Resources

Reading Assignment and Discussion Questions on Boston Marathon Attack

Mental Health and Disasters: How Your Body Reacts During and After a Tragedy

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An envelope addressed to Sen. Roger Wicker, R-Miss., tested positive for ricin at the U.S. Capitol's off-site mail facility today. Photo by Drew Angerer/ Getty Images.

WASHINGTON -- An envelope addressed to Sen. Roger Wicker of Mississippi twice tested positive Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three and left more than 170 injured at the Boston Marathon.

One senator, Claire McCaskill of Missouri, said authorities have a suspect in the fast-moving ricin case, but she did not say if an arrest had been made. She added the letter was from an individual who frequently writes lawmakers.

The FBI and U.S. Capitol Police are both investigating. Both declined to comment.

Late Tuesday, Wicker released a statement acknowledging the letter and said it was sent to his Washington office.

"This matter is part of an ongoing investigation by the United States Capitol Police and FBI," Wicker said. "I want to thank our law enforcement officials for their hard work and diligence in keeping those of us who work in the Capitol complex safe."

Terrance W. Gainer, the Senate sergeant-at-arms, said in an emailed message to Senate offices that the envelope to Wicker, a Republican, had no obviously suspicious outside markings and lacked a return address. It bore a postmark from Memphis, Tenn.

Mail from a broad swath of northern Mississippi, including the Memphis suburbs of DeSoto County, Miss., Tupelo, Oxford and the northern part of the Mississippi Delta region is processed and postmarked in Memphis, according to a Postal Service map. The Memphis center also processes mail for residents of western parts of Tennessee and eastern Arkansas.

Gainer said there was "no indication that there are other suspect mailings." Yet he urged caution, and also said the Senate off-site mail facility where the initial tests were performed on the letter will be closed for a few days while the investigation continues.

The letter was discovered at a mail processing plant in Prince George's County in suburban Maryland, according to Sen. Dick Durbin, D-Ill.

Wicker, 61, was appointed to the Senate in 2007 and won election to a full term two years ago. He previously served a dozen years in the House.

He has a solidly conservative voting record, so much so that he drew notice last week when he voted to allow debate to begin on controversial gun legislation in the Senate. "I cast this vote at the request of the National Rifle Association, of which I am a member," he said in a statement at the time that added he has a 100 percent voting record in favor of Second Amendment rights.

Majority Leader Harry Reid told reporters of the letter. Other lawmakers said they had been provided information by Gainer's office.

Milt Leitenberg, a University of Maryland bioterrorism expert, said ricin is a poison derived from the same bean that makes castor oil. According to a Homeland Security Department handbook, ricin is deadliest when inhaled. It is not contagious, but there is no antidote.

"Luckily, this was discovered at the processing center off premises," Durbin said. He said all mail to senators is "roasted, toasted, sliced and opened" before it ever gets to them.

One law enforcement official said evidence of ricin appeared on two preliminary field tests of the letter, although such results are not deemed conclusive without further testing. The official spoke on condition of anonymity because the investigation remains active.

The discovery evoked memories of the days after the terrorist attacks of Sept. 11, 2001, when mail laced with anthrax began appearing in post offices, newsrooms and congressional offices.

That included letters sent to Sen. Tom Daschle, D-S.D., who was Senate majority leader, and Sen. Patrick Leahy, D-Vt. Two Senate office buildings were closed during that investigation.

Overall, five people died and 17 others became ill. The FBI attributed the attack to a government scientist who committed suicide in 2008.

More immediately, though, the discovery came as lawmakers were demanding answers to the attacks in Boston a day earlier.

There was no evidence of a connection between the bombings and the letter addressed to Wicker.

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Hari Sreenivasan talks with Rev. Samuel Rodriguez about the changing debate over immigration.

The last time the nation heard the terms "amnesty" and "pathway to citizenship" batted around with such frequency was seven years ago, in the year leading up to the ultimately doomed Immigration Reform Act of 2007. The bill was a compromise championed by then-President George W. Bush that called for stronger border security and workplace enforcement laws, and would have led to legal status for immigrants in the U.S. without documentation.

The arguments on both sides sounded a whole lot like they do today. At the time, the NewsHour ran a series of one-on-one discussions, called "Immigration Insights," with individuals exploring the concept of reform through the lens of their own involvement with immigrants.

Today, with comprehensive reform once again reportedly around the corner, we decided to go back to some of the same individuals (along with some new faces) and ask what's changed -- and what hasn't -- seven years later. Does today's political landscape feel like history repeating itself? Have their attitudes toward immigration changed?

The role of faith has long factored into the debate over illegal immigration in this country. In 2006, Ray Suarez interviewed Archbishop Charles Chaput of Denver about a series of town hall meetings he had been moderating to help explain the church's position on the immigration debate. You can watch that interview below.

Ray Suarez speaks with Archbishop Charles Chaput on Aug. 15, 2006.

"The church has a long tradition of social justice teaching," Chaput explained at the time. "The church is not in favor of illegal immigration. The church is not in favor of breaking the law. The church is in favor of changing the laws so that they work, they make sense, and that they serve the common good and everyone's dignity."

Archbishop Chaput was unavailable to participate in today's Google Hangout, but Hari Sreenivasan connected with Reverend Samuel Rodriguez, president of the National Hispanic Christian Leadership Conference. With more than 40,000 member churches, it's the country's largest Hispanic Christian organization.

Rodriguez says the role of faith "speaks to the radical transformation" of the immigration debate from 2006 to 2013. Seven years ago, he says, the majority of people "viewed immigration as a political issue," one in which the faith community was "not necessarily engaged."

But the faith community has learned from the failures of 2006, he says. "We spoke to pastors across the country. We targeted the 24 largest cities in America, met with white Evangelical pastors, African-American pastors, sat down with them and said, 'This is not a political issue, it is a moral issue.'"

"We may very well be deporting the future of American Christianity." --Rev. Samuel Rodriguez

Rodriguez says the increasing number of Hispanics in the church has forced pastors nationwide to sit up and take notice.

"Our churches are filled with undocumented individuals," he says. "We may very well be deporting the future of American Christianity."

Rodriguez, who worked with the George W. Bush administration on their unsuccessful reform efforts in 2006, describes his outlook this time around as "a sense of uber-optimism with an inner lining of prayerful caution." And after meeting with President Barack Obama earlier this month, "All the stars have definitely lined up." He added, "It's just a matter of whether we have the political will now, as a nation, to push this forward."

Related Content:

The Evolving Immigration Debate: Border Security

The Evolving Immigration Debate: Guest Workers

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Click to enlarge.

A man looks at "MaskII" by Ron Mueck at the Fondation Cartier pour l'Art Contemporain in Paris. The Australian artist's work is on view through Sept. 29. Photo by Thomas Coex/AFP/Getty Images.

Former Rep. Gabrielle Giffords, D-Ariz., and her husband Mark Kelly arrive at the Capitol Tuesday with Sens. Pat Toomey, R-Pa., left, and Joe Manchin, D-W.Va. Photo By Bill Clark/CQ Roll Call.

Emotional appeals. A tense week on Capitol Hill. A moment of truth, for some.

The Senate on Wednesday will begin voting on a series of amendments to a sweeping gun control package. And most indications are that advocates for expanding a background check system for gun purchases -- a key provision of the bill -- are several senators short of their goal.

"We will not get the votes today," Sen. Joe Manchin, D-W.Va., told NBC's Kelly O'Donnell on Wednesday.

On MSNBC's "Morning Joe," Manchin said he has "over 90 percent" of Senate Democrats on board and needs just nine Republicans to join them to secure the 60 votes for his compromise measure. A statement released by his spokesman Wednesday morning said: "Senator Manchin remains optimistic and hopeful ... I see no reason to bet against [him] today. He will continue to explain his bill to his colleagues and anyone with concerns until the minute they vote."

But nine votes, at this point, seems impossible.

Still, the NRA is out with a last-minute ad urging senators to vote against expanded background checks. The spot mocks New York City Mayor Michael Bloomberg.

"Tell your senator listen to America's police instead of listening to Obama and Bloomberg," the narrator says.

Watch here or below.

The advocacy doesn't stop there.

We hear that eyes were glistening during a party caucus meeting, as Manchin outlined the amendment forged with Sen. Pat Toomey, R-Pa. He asked some of the Democratic holdouts -- including Arkansas Sen. Mark Pryor and Alaska Sen. Mark Begich to back their measure.

Senators talked about gun-related tragedies in their states, from Newtown, Conn., to the Virginia Tech massacre.

Former Rep. Gabrielle Giffords of Arizona and her husband Mark Kelly were there too, highlighting the gun control movement's urgency.

Vice President Joe Biden urged his former colleagues to deliver. Senators gave few details publicly, saying instead it was an "emotional" meeting. Roll Call's Meredith Shiner and Jonathan Strong set the day's scene:

Kelly and Giffords appeared before Senate Democrats -- including six still undecided on the measure -- at the caucus's weekly policy lunch. They later addressed a bipartisan crowd at the dedication of a room in the Capitol Visitor Center to slain Giffords staffer Gabriel Zimmerman, one of six people shot and killed in the 2011 Arizona mass shooting that rendered Giffords incapable of continuing her congressional service.

The poignant ceremony was marked by moments of awkwardness, as Kelly noted in his remarks the destructive power of high-capacity magazines that Congress cannot find enough votes to restrict.

Giffords' friend, Sen. Jeff Flake, R-Ariz., was also at the ceremony, a day after he announced he could not support the bipartisan background check agreement.

Late Tuesday afternoon, Sen. Dean Heller of Nevada, who was one of three Republicans left on the board, announced he would not support the deal.

Kelly told reporters Tuesday that his group would work to replace the freshman senator if he votes "no" on gun legislation that would expand background checks, despite his strong friendship with Flake. He added that it seemed like Flake hadn't read the proposal.

The Senate still plans to forge ahead.

Here's the basic layout of the series of votes expected to begin Wednesday at 4 p.m. ET. Each needs 60 votes to pass.

Manchin-Toomey amendment on background checks

Limiting gun trafficking

Sen. John Cornyn's amendment "to allow reciprocity for the carrying of certain concealed firearms."

Assault weapons ban

Sen. Richard Burr's amendment "to protect the Second Amendment rights of veterans and their families."

Banning high-capacity magazines

Sen. John Barrasso's amendment to withhold 5 percent of Community Oriented Policing Services program federal funding from States and local governments that release sensitive and confidential information on law-abiding gun owners and victims of domestic violence.

Sen. Tom Harkin and Sen. Lamar Alexander's amendment relative to mental health.

Manchin and others have said that even if the background checks measure fails Wednesday, their push is far from over. They also hail the day's events as momentous, given it's been decades since any major gun legislation passed Congress.

BOSTON REACTIONS CONTINUE

The FBI continues to investigate the explosions in Boston, with as few answers as the day before.

President Barack Obama spoke Tuesday:

Given what we now know about what took place, the FBI is investigating it as an act of terrorism. Any time bombs are used to target innocent civilians it is an act of terror. What we don't yet know, however, is who carried out this attack, or why; whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual...

It will take time to follow every lead and determine what happened. But we will find out. We will find whoever harmed our citizens and we will bring them to justice. We also know this -- the American people refuse to be terrorized.

He encouraged citizens to contact authorities if they see anything suspicious in the coming days and promised more updates once investigators learned more information. The White House also announced that Mr. Obama will speak Thursday at an interfaith service in Boston.

The NewsHour offered extensive coverage Tuesday of the situation.

Kwame Holman walked through the facts in a video piece, and Jeffrey Brown received updates from a public radio reporter in Boston.

Social media producer Colleen Shalby rounded up some of the tributes from news organizations, sports stars and others that have surfaced online.

Hari Sreenivasan spoke with the head of Massachusetts General Hospital's emergency medicine, who described how the hospital has treated patients and noted that one trauma surgeon ran the marathon and then reported to the operating room.

That conversation is here or below:

Gwen Ifill spoke with a former investigator and a terrorism expert to gain fuller sense of the authorities' approach. Science reporter-producer Jenny Marder pointed out in this blog post the bombs were likely homemade rather than military-grade or dynamite, because of the lighter color of their smoke. Watch Gwen's conversation here or below.

Christina talked with Howard Kurtz and Lauren Ashburn from the Daily Download team about how the Internet became a place for both helping and healing, and found the world showing an outpouring of love for Boston.

If you're curious about some of the Twitter and Facebook memes they mentioned, and ones they didn't, this Snopes post explains the backstories.

Watch the segment here or below:

In a related story, one Boston Marathon runner used Facebook to try and help track down a couple who consoled her after the blast. They gave her their medal for crossing the finish line, and she wants to return it. And we highly recommend reading this incredible story from the New York Times' Tim Rohan the before and after of the moment captured in one of the bombings' most notable photos.

LINE ITEMS

A letter addressed to Sen. Roger Wicker, R-Miss., twice tested positive for the potentially fatal poison ricin, Senate Majority Leader Harry Reid, D-Nev., confirmed late Tuesday. Sen. Claire McCaskill told reporters Tuesday the person who sent the letter frequently writes to senators.

Bloomberg News reveals how White House homeland security and counterrorism adviser and Boston-area native Lisa Monaco handled news of the bombings with Mr. Obama, while receiving messages from home. National Journal's Sara Sorcher also profiles Monaco, who's been on the job about a month.

Mr. Obama will have dinner this time with a dozen Democratic senators at the Jefferson Hotel Wednesday night.

Opponents of the Gang of Eight's immigration bill are reviving tactics that killed a 2007 bill, namely slowing the debate in order to introduce "poison pill" amendments to divide fragile bipartisan support.

The New York Times explains how Democratic senators formed the immigration Gang of Eight over jelly beans, pizza and chocolate-covered matzo, and in the Senate gym. Ashley Parker writes the full backstory.

Talking Points Memo's Benjy Sarlin breaks down in detail the pathway to citizenship provisions in the immigration bill.

The American Conservative Union issued a positive statement about the bipartisan immigration legislation.

The Washington Post front-pages a story about Facebook flexing its political muscle on immigration reform.

Budget Committee Chairman Rep. Paul Ryan, R-Wis., said Tuesday he won't seek a conference committee to negotiate differences between the House and Senate budgets until lawmakers privately come closer together.

Don't miss Ryan Reilly's reporting and photos from Gitmo for Huffington Post.

In the first half of an interview with NBC's "Today Show," recorded Monday, Mr. Obama said the United States should be prepared for "every contingency out there" in regards to North Korea. The second half of the interview aired Wednesday.

Terry McAuliffe will skip the annual shad planking in Virginia this year. What's a shad planking? We're glad you asked.

Politico notices that some lawmakers tied the response in Boston to the sequester.

Former South Carolina Gov. Mark Sanford is set to appear in family court just two days after South Carolina 1st Congressional District's May 7 special election after trespassing on his ex-wife's property, according to reports late Tuesday. "I am doing my best not to get in the way of his race. ...I want him to sink or swim on his own...but he makes things difficult for me when he does things like trespassing," said Jenny Sanford.

Four years after its debut, the tea party has declined in popularity, but not without having been co-opted by elements of the Republican Party that have left a mark on American politics, writes NBC's Mark Murray.

On Tuesday, Virginia Tech observed the sixth anniversary of the deaths of 32 students and professors after a student opened fire in a classroom on the campus in 2007. Colin Goddard, one of the students who survived the attack has become a spokesman for efforts to expand background checks on gun sales. He recently spoke with Kwame Holman about this effort.

Iowa Republican Rep. Steve King's meager first quarter haul of $93,000 is casting doubts on speculation he's eyeing retiring Sen. Tom Harkin's seat in 2014.

Chris Dodd, chairman of the Motion Picture Association of America, announced a campaign Tuesday to promote a change to ratings tags designed to give audiences more details on why a film received its "R," "PG-13" or "PG" rating. Tags for trailers also will include content descriptors showing they have been approved to play with the feature film. The tweaks follow meetings in January that Dodd and John Fithian, chairman of the National Association of Theatre Owners, held with Biden as part of an effort to provide better information to parents about the level of violence in a movie. The Classification and Ratings Administration also has created a Twitter feed that provides a movie's rating and describes the content that led to the rating.

Syria Deeply journalist Karen Leigh talked with Diane Foley, the mother of American journalist Jim Foley, who has been missing in Syria for five months.

More than 97,000 people think Nicholas Cage should be in possession of the Declaration of Independence.

This story about a New Hampshire Republican state lawmaker's label for females also reads like a "What not to do."

For a lighter moment, how about this NPR story on why we stand where we stand in a crowded elevator.

NEWSHOUR ROUNDUP

Marcia Coyle of the National Law Journal outlined an interesting case argued before the Supreme Court Tuesday about tribal law, specifically the Indian Child Welfare Act of 1978, and child custody. The case has become known by the child's name, Baby Veronica, and asks the Supreme Court to decide the dispute between the South Carolina family that intended to adopt her and her biological father, a man who is part Cherokee.

Hari and coordinating producer Elizabeth Summers covered the immigration debate from one man's perspective as part of their series of conversations with individuals affected by policy. Hari spoke with South Carolina peach farmer Chalmers Carr in a Google Hangout.

The leader of the nation's largest Hispanic Christian organization tells Hari he has "a sense of uber-optimism with an inner lining of prayerful caution" about the prospects for comprehensive immigration reform this year. Watch that conversation here.

TOP TWEETS

As always, the Senate is just a tedious exercise in delaying the inevitable. Have fun making ads off failed votes today, boys.

— Meredith Shiner (@meredithshiner) April 17, 2013

I'm often proud to be a reporter. Today I'm even prouder to be a reporter at The Boston Globe, giving much context to hard-to-understand day

— Matt Viser (@mviser) April 16, 2013

If you're in Boston without phone service, use this website to call your family bit.ly/ZxEyPe by @twilio#BostonMararthon

— Robert Hernandez (@webjournalist) April 16, 2013

Governor and staff in Beijing observing moment of silence on Virginia Tech Remembrance Day -staff twitter.com/BobMcDonnell/s...

— Bob McDonnell (@BobMcDonnell) April 16, 2013

.@wholefoods...Who's the bigger menace - @timryan or Kim Jong-un? But seriously, congrats on the recognition, Tim! twitter.com/PatrickMcHenry...

— Patrick McHenry (@PatrickMcHenry) April 16, 2013

Overlooked in Q1 fundraising reviews - @johncornyn& @team_mitch out-raised almost every 2014 Democrat. Steep climb got steeper for Dems.

— Brian Walsh (@brianjameswalsh) April 16, 2013

Cassie M. Chew and politics desk assistant Simone Pathe contributed to this report.

For more political coverage, visit our politics page.

Sign up here to receive the Morning Line in your inbox every morning.

Questions or comments? Email Christina Bellantoni at cbellantoni-at-newshour-dot-org.

Follow the politics team on Twitter:

Follow @cbellantoni

Correction: Sen. Joe Manchin told NBC's Kelly O'Donnell on Wednesday, "We will not get the votes today" on the background checks amendment. Manchin did not make that statement on MSNBC's "Morning Joe."

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First responders tend to the wounded, including a young boy in a wheelchair, where two explosions occurred along the final stretch of the Boston Marathon on Monday.

Dr. David Mooney sees bleeding children all the time. As director of the trauma program at Boston Children's Hospital, he knows how to soothe overreacting kids and their parents, and most times "the wounds aren't quite as bad as advertised," he said.

Monday was different. Monday left him speechless. The children being hauled into Boston Children's Hospital didn't need to say a word to express the severity of the explosions near the finish line of the Boston Marathon.

"The first two that came in had soot on their faces, singed eyebrows, burned hair, tourniquets on their legs that were clearly preventing so much blood loss it would have been a death sentence without them," he said. "There were nails sticking out of a young girl's flesh, just poking through the skin."

'It's not unusual that the mental health issues will last a lifetime.' -- Dr. David Mooney

Shrapnel still remains lodged in the muscles of some of them -- waiting to be removed on a day when the doctors aren't in life-saving mode. Like many of the victims of Monday's terrorist attack in Boston, the long recovery for these children has only begun. Physical wounds will take months, if not a year or more, to heal, Mooney said. And in a case like this, "it's not unusual that the mental health issues will last a lifetime."

In emergency rooms throughout Boston, the controlled chaos looked much the same, with shards of metal, nails and ball bearings being carefully removed from the ankles, calves and thighs of many victims, which now includes three dead and more than 170 wounded. At Massachusetts General Hospital, Dr. George Velmahos said the wounds were so severe that many of his patients were "automatic amputees," and that doctors "just completed what the bomb had done."

Across town, at St. Elizabeth's Medical Center -- a facility more accustomed to treating marathon fatigue victims due to its proximity to "Heartbreak Hill" -- emergency department chief Dr. Mark Pearlmutter and his team spent have much of their time removing chunks of metal and "what turned out to be ball-bearing components" from flesh and muscle.

But even many hours after the blast, the emotional gravity of what that meant was still sinking in for victims. While Pearlmutter noticed some trying to cling to the "very good mood" from the festival atmosphere of Patriots' Day, he treated others who were "petrified" to step outside again. One of the wounded first responders he met couldn't shake the realization that his post near the finish line was about eight feet from the second bomb. On the verge of a panic attack, the patient kept "wondering whether he should have seen something sooner," Pearlmutter said. "The survivor's remorse he was experiencing was terrible."

Terrible and likely to continue for some time, if similar terror attacks in other parts of the world are a guide, said Dr. Arieh Shalev, a professor of psychiatry at New York University's Langone Medical Center.

In Jerusalem, Shalev saw "very similar events occurring frequently -- shocking, traumatizing and totally unexpected," while he was serving as the chair of psychiatry at Hadassah University Hospital in Jerusalem. Those attacks happened in public places and targeted random bystanders -- just like in Boston, he said.

And just like in Jerusalem, Post-Traumatic Stress Disorder is the likely long-term result for some. While Shalev warned against early diagnoses, he also said that victims "should be managed in some form very early on." Anyone who was in or near the blast should be monitored closely and encouraged to communicate how they're feeling at both a physical and emotional level.

"If they're in pain, the pain should be the primary target. If they need to talk to someone, they should be allowed to do that," Shalev said. "Reducing the stressfulness of the event itself by whatever means possible should be at the core -- so that it doesn't progress further."

Physicians are also on the lookout for another covert disorder that could have been triggered by the improvised explosive devises: hearing loss. The double blasts created a pressure wave on Boylston Street that ricocheted off the buildings, leading to hearing problems for some of those in the crowd.

Dr. Alicia Quesnel, an ear specialist at the Massachusetts Eye and Ear Infirmary, has seen a steady stream of patients complaining of ear pain and ringing since the blasts. Those symptoms are often traced to holes in the ear drum itself, injury to the bones in the middle ear and damage to the nerves in the inner ear, Quesnel said. Anyone experiencing the telltale signs of hearing damage -- including ear pain, continuous ringing, blood drainage or dizziness -- should be examined as soon as possible, she said.

'Some of the principles we've learned from those conflicts (in Iraq and Afghanistan) -- pain control, how to help people use prosthetic limbs, how to treat concussive blasts and head injury -- all of those lessons are going to serve us well here.' -- Dr. Ross Zafonte

As the true toll for Monday's attacks continue to become more clear -- and as the response moves from crisis and surgery to long-term care -- another group of Boston health care providers is preparing for the recovery phase.

None of the victims have moved to Harvard's Spaulding Rehabilitation hospital yet but the facility is preparing the beds. Dr. Ross Zafonte, the hospital's vice president of medical affairs, said the facility is well-equipped to teach the victims of the Boston Marathon bombings how to do things they considered basic just days ago, like how to walk -- or perhaps for some, even how to eat and talk.

The facility developed many of its techniques after treating veterans wounded in Iraq and Afghanistan, many of whom were also injured by an improvised explosive device.

"Some of the principles we've learned from those conflicts -- pain control, how to help people use prosthetic limbs, how to treat concussive blasts and head injury," Zafonte said, "all of those lessons are going to serve us well here."

Spaulding's mental health unit will also help patients come to terms mentally with what happened as they work to rebuild their lives. True PTSD often emerges 30 days after event, especially as numbness and shock wear off and a full range of emotional responses return. It will be one of center's biggest tasks, Zafonte admits.

For now, the chaos of the moment is serving as a temporary ointment in itself. At Brigham & Women's Hospital, Dr. Parveen Parmar and her team have been so busy treating wounds that she says few have taken time to process what they've seen.

"I think eventually we'll have a little bit more time to deal with that piece of it," she said. "But not yet."

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Tugboat Gatun, first boat to enter the Panama Canal in 1913, passing through the west chamber. Photo by Time Life Pictures/Getty Images.

It isn't often that a visiting Latin American political leader starts a talk to a Washington audience reciting verses from English poet John Keats. But Panamanian presidential candidate Juan Carlos Navarro tends to wax lyrical whether talking about his country's bounty of flora, fauna and rare birds or one of the most thriving economies of Latin America with a growth rate between 8 and 10 percent. (Panama also has become a major retirement destination for Americans, who can live on $1,200 a month on a currency aligned with the dollar and in a largely bilingual society without learning much Spanish.)

And if there is a consistent thread between poetry and the economy, it is Panama's geography, a Central American isthmus slightly larger than South Carolina that has served as a bridge or pathway between the Atlantic and Pacific oceans.

Panama's discovery by European explorers in the 1500s, which provoked a Keats poem three centuries later attributing the sighting incorrectly to Cortez rather than Balboa, has been the country's blessing and curse since, especially in its relations with the United States.

The appearance of the 51-year-old former Panama city mayor Navarro, a graduate of Dartmouth and Harvard University, at ease in colloquial English is one more sign that relations with the U.S. are in a period of calm. Quite a contrast to the storms that have brewed since Theodore Roosevelt helped push Panama to separate from Colombia, then accept an American built and owned canal, which only reverted to Panamanian control after nationalist rioting in the 1960s, a Carter administration treaty barely ratified by the U.S. Senate and the U.S. ouster of military strongman Manuel Noriega in the first Bush administration.

A second canal is set to open by the end of 2015, one year behind schedule and over budget, in contrast, Navarro said, to the first U.S. canal that came in under budget and a year ahead of schedule. But at considerably smaller human cost than the first canal, whose death toll by accident and disease numbered several thousand. The new $5 billion canal, he added, is part of the web of Panamanian connections -- by sea, air, rail and highway to the rest of Latin America that helps make the country a major regional commercial and banking hub.

Navarro insisted "Panama's economic miracle is based on an open economy and democratic beliefs." But he acknowledged that at least 25 percent of the country's 3.5 million people still live below the poverty line and that the country's education system is rated among the world's worst, especially for Afro-Panamanians and indigenous citizens.

The businessman and environmentalist told the Inter-American Dialogue audience that outside his country he would not criticize the government of President Ricardo Martinelli, elected in 2009. His measured stance was in sharp contrast to an appearance by Martinelli's vice president Juan Carlos Varella at a Washington conference last year.

Varella's party had dropped out of the ruling coalition, and he sharply criticized the president for suppressing democratic institutions and press freedoms as thousands of Panamanians were taking to the street, successfully winning a rollback of proposed election law changes.

Navarro's PRD party is the same one that brought nationalist leader Omar Torrijos to power in the 1970s and his son Martin Torrijos as the third democratically elected president since Noriega's ouster. In contrast to their nationalist populism, Navarro would make only a glancing joke about the U.S. budget deficit and said his challenges, if elected, would be to reform the country's judicial system and keep the budget balanced while pushing programs for education and to aid the poor.

He noted that every presidential election since Noriega's departure has been won by a different political party.

"Thank the Lord," Navarro commented on that augury for his political prospects.

And for poetry buffs, here is the excerpt from Keats' "On First Looking into Chapman's Homer", recited by Navarro:

Then felt I like some watcher of the skies When a new planet swims into his ken; Or like stout Cortez, when with eagle eyes He stared at the Pacific -- and all his men Looked at each other with wild surmise -- Silent, upon a peak in Darien.

Michael D. Mosettig, PBS NewsHour foreign affairs and defense editor emeritus, watches wonks push policy in Washington's multitude of think tanks. From time to time, he writes dispatches on what those scholars and wannabe secretaries of state have in mind for Europe, Asia and Latin America.

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The funeral of Britain's former Prime Minister Margaret Thatcher in London on Wednesday brought out dignitaries and protesters alike.

Supporters Gather

Members of the public hold signs, including this one saying "Thank you, Britain's fighting lady", along the sidelines of the funeral procession for former British Prime Minister Margaret Thatcher on April 17 in London. She died April 8 following a stroke at age 87. Photo: Karwai Tang/WireImage

Extra Security

Armed police lined the route of Margaret Thatcher's funeral procession, where dignitaries from around the world gathered on April 17. Authorities said security was boosted at the event following the dual explosions at Monday's Boston Marathon. No one has claimed responsibility for that attack, which killed three people. Photo: Warrick Page/Getty Images

Thatcher's Family

The family of Margaret Thatcher watches as her casket passes. From the left are Thatcher's daughter Carol Thatcher and her partner Marco Grass; Sarah Thatcher, the wife of son Mark Thatcher; and his children Michael and Amanda, who delivered one of the readings at the ceremony. Photo: Mark Cuthbert/UK Press via Getty Images

Funeral Ceremony

Margaret Thatcher's funeral service with military honors was held at St. Paul's Cathedral in London. Photo: Stefan Wermuth - WPA Pool/Getty Images

Queen Attends

Among the dignitaries attending Margaret Thatcher's funeral were Queen Elizabeth II and Prince Phillip, duke of Edinburgh (pictured here). Representing the United States were former secretaries of state George Shultz and James Baker; Barbara Stephenson, charge d’affaires to the UK; and Louis Susman, former ambassador to the UK. (See Shultz's and Baker's recollections of working with the "Iron Lady".) Photo: Paul Edwards - WPA Pool/Getty Images

Protesting Thatcher

Protesters display an effigy of Margaret Thatcher in a coffin in Goldthorpe, northern England, on the day of her funeral April 17. Thatcher is considered one of Britain's most influential and divisive prime ministers for her efforts to bring the UK out of its economic slump. (Read more worldwide reaction to Thatcher's death.) Photo: Andrew Yates/AFP/Getty Images

By Judi Henderson-Townsend and Cynthia Mackey

"Seniorpreneurs" Judi Henderson-Townsend, owner of Mannequin Madness, and Cynthia Mackey, founder of Baby Boomer Business Owner.

Paul Solman: Mannequin Madness. That's where we met Judi Henderson-Townsend and Cynthia Mackey -- at Townsend's "body shop" in Oakland, Calif., a few weeks ago. We were shooting a story on "senior" entrepreneurs and though both looked young enough to be my daughters, both are in their 50s. That makes these budding entrepreneurs surprisingly long of tooth by traditional standards.

Traditional standards, however, haven't kept up with the economy, or the Baby Boom, or both. We seem to be entering an era of new firms run by "old" entrepreneurs.

Here are the pair's 10 Tips for Senior Entrepreneurs.

Cynthia Mackey and Judi Townsend: Paul asked that we introduce ourselves. So when we first started our businesses, we were both refugees from corporate America and we were both over 40. Cynthia had a history of entrepreneurship in her family while Judi fell into it. We both started bootstrap ventures, with far more passion than capital.

Cynthia had been working as a technology consultant and saw a niche to fill in training baby boomers to use social media to grow business. She launched BabyBusinessBoomerBusinessOwner.com as a means to do just that. Judi, by contrast, was an accidental entrepreneur. While purchasing a mannequin for an art project, she stumbled across a mannequin vendor who was going out of business, bought his inventory on a whim, and launched MannequinMadness.com.

While we came to our businesses in different ways, we discovered that we were on the leading edge of the same new trend -- senior entrepreneurship. The tips below are based on our experience of being and hiring senior entrepreneurs.

According to SmartBizTrends.com, the new face of start-ups is a senior citizen. If you are thinking of starting a business, here are 10 tips from two "seniorpreneurs".

1. You Are Never Too Old to Start a Business Think it's foolhardy to start a business because you're a senior? People age 55-64 have a higher rate of entrepreneurial activity than those age 20-34. Check out these successful seniorpreneurs.

2. Turn Passion into Profit No idea is too odd to find success, as these 10 off-the-wall businesses demonstrate. Building a business ignited by your passion fuels the time and energy required to propel you to success. Yes, more than passion is a necessity, but without it, your desire to get through peaks and valleys will wane and that will affect your business overall.

3. Build a Community of Positive Influences Being an entrepreneur at any age is daunting. Seek out people and resources who will encourage you to "go for it" instead of naysayers. In April, the Small Business Administration (SBA) and AARP are sponsoring National Entrepreneur Mentor Month at offices throughout the country as well as online. Senior Entrepreneurship Works is a nonprofit organization designed to help seniors aged 50-plus build sustainable businesses.

4. Make your Workspace Fit Your Lifestyle Owning a business no longer requires leasing an office space or storefront. You can set up an online store with sites like Etsy, Ebay and BigCommerce to sell your products online. If your business does require an office, co-working spaces are flexible and cost-effective options. As long as you have Internet access, you can connect with your customer, staff or sales data from anywhere.

5. Staff as you Grow with Freelancers You can find talented independent contractors to do short or long term projects for your business on an as-needed basis. This helps manage your costs, while growing your business revenues. If you can't find the talent you need locally, here are the 20 best online sites to find virtual assistance.

6. Be Innovative with Your Funding Sources Before you raid your savings, consider grants, contests and crowdfunding. This 89-year-old grandmother utilized Kickstarter to fund her decorative walking cane business. The Purpose Prize awards $100,000 to social entrepreneurs who start their business after age 60. The U.S. General Services Administration has a list of challenges to award business owners who solve specific problems. Create Google alerts to get information on business contests emailed to you.

7. Go Back to Class The idea of being a student again might seem like a drag but if you need to beef up your business acumen the good news is you can now learn from the comfort of your living room. Podcasts, webinars, tele-seminars, ebooks, YouTube videos and slideshows are the new "teachers" enabling you to learn about any business subject.

8. An Internet Presence is a Must Even if most of your customers are by referral, you can give your business a boost by getting a website or blog. A whopping 97 percent of Internet users look for local goods and services online. It is easier than ever to get your business online with tools like Wix, Weebly and Wordpress. Google and Intuit have partnered to offer Get Your Business Online, a website enabling small business owners to create a free website through 2013.

9. Your Mobile Device is now a Pocket Office Your smart phone or tablet now gives you the ability to receive an email order, contact a customer and take a payment all at once, changing the paradigm of what point of sale means. There are numerous applications you can download which are invaluable for running your business. And with tools such as the Square you can process credit/debit payments on your mobile device.

10. Use Social Media for Word of Mouth Marketing Select the best network for your customers and one that you can maintain consistently. It's better to be effective on one network, than ineffective on all. Look for social media workshops hosted by the SBA or the Small Business Development Center in your region. Or learn online via courses such as Baby Boomer Business Owner and Lynda.com.

PBS NewsHour Economics Correspondent Paul Solman reports on late bloomers who decided to take the plunge into self-employment. Watch his full report above.

Judi Henderson-Townsend is the owner of Mannequin Madness, an award-winning small business that rents, sells and recycles mannequins.

Cynthia Mackey is a tech-savvy online marketer and founder of BabyBoomerBusinessOwner.com, a website offering courses on how small business owners can use social media to grow their business.

This entry is cross-posted on the Rundown -- NewsHour's blog of news and insight. Follow @paulsolman

View a slideshow of Thatcher's funeral.

Six black horses pulled the union jack-draped casket of Britain's influential and controversial former Prime Minister Margaret Thatcher to her funeral service Wednesday complete with military honors.

Thatcher, who served as Conservative party prime minister from 1979 until 1990, died April 8 following a stroke at age 87.

Among the dignitaries attending her funeral at St. Paul's Cathedral in London were Queen Elizabeth II and Prince Phillip, duke of Edinburgh. Former secretaries of state George Shultz and James Baker, who had worked closely with Thatcher, led the U.S. delegation. Former Vice President Dick Cheney, former Secretary of State Henry Kissinger, and former House leader Newt Gingrich also paid their respects.

The ceremony brought out supporters, who held signs praising "Britain's fighting lady", and protesters, who turned their backs at Ludgate Circus along the funeral procession route. Thatcher faced criticism for her handling of Britain's economic troubles during her time in office.

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A lot has happened to Kelly Oxford since we first spoke to her on Art Beat three years ago. The Canadian stay-at-home-mom-turned-Twitter-phenom has capitalized on the whit that gained her Internet fame.

Oxford moved her family to Los Angeles, began writing pilots for major TV networks, penned a screenplay slated to be a movie directed by Drew Barrymore, and earlier this month published her first book, which is now a New York Times best-seller.

In the memoir, "Everything Is Perfect When You're a Liar," Oxford describes herself as smart, but lazy, a trait which she says makes her efficient. That helps when crafting funny observations in just 140 characters and, it turns out, saved her from wasting time when writing her 300-page book.

"I didn't waste any time ever writing manuscripts that were never bought or writing pitches or anything like that for anybody else to tell 'yes' or 'no,'" Oxford said in a recent phone conversation. "I always just put out my own material, and along the way I was becoming a better writer because I was learning whom my audience was and what they liked."

Though she never went to college, Oxford began writing at an early age, creating a fake newspaper for her neighborhood that covered fictional murders and pets that had been eaten. Or, as described in the book, re-writing "Star Wars" as a play for her friends to perform. She started an anonymous blog more than 10 years ago after spending a lot of time online and realizing that places for mothers to communicate with each other weren't very entertaining. When MySpace came around, she dropped the anonymity and concentrated on being a funny writer.

"Being funny on the page is much easier for me than being funny in person, just because I don't have that urge inside of me to entertain, you know, physically or be on the stage or anything like, but I still do feel the urge to entertain and I have since I was a child," Oxford said.

Her family is a frequent inspiration, like in this recent Tweet:

4 yr old thinks I'm an idiot for not knowing how to do her rollerblades up, but I think she's an idiot for wanting to rollerblade.

— kelly oxford (@kellyoxford) April 7, 2013

They also provide fodder for the last chapters of the book.

"By the time we're adults we know what people want to hear. We know what will work in a conversation," Oxford said. "Throughout our life we've learned all of these rules and kids don't know those rules so they'll basically blurt out anything at any time. Occasionally its very embarrassing as an adult to hear it, but it's always so funny because it comes from such an innocent place."

The late Roger Ebert was an early fan of Oxford and helped promote her work, even writing a letter to the U.S. government to help her with her work visa.

"I wasn't getting paid for my work, but then to have somebody like Roger say, you know what, you're doing a really great job, was sort of the beginning for me, to know I was entertaining the entertainers," Oxford said. "It meant a great deal to me to have him on my side and I always loved that the dirtier, the raunchier the Tweet, the quicker he was to re-Tweet it, and I loved that about him very much."

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WASHINGTON -- Letters sent to President Barack Obama and a Mississippi senator that tested positive for poisonous ricin are related and both are postmarked Memphis, Tenn., the FBI said Wednesday. A senator said police have a suspect in mind. Several other reports of suspicious mail to government officials were being checked.

In an intelligence bulletin obtained by The Associated Press, the FBI says that letters to Obama and Sen. Roger Wicker, R-Miss., both say: "To see a wrong and not expose it, is to become a silent partner to its continuance." Both letters are signed, "I am KC and I approve this message."

The activity came as tensions were high in Washington and across the country following the deadly bombings on Monday at the Boston Marathon that killed three people and injured more than 170. The FBI said there is no indication of a connection between the letters and the bombing. The letters to Obama and Wicker were postmarked April 8, before the marathon.

Sen. Claire McCaskill, D-Mo., said that police suspect a person who "writes a lot of letters to members." She made the comment Tuesday as she emerged from a briefing by law enforcement on the Boston bombing. Authorities declined to comment on a suspect. In addition to the letters, U.S. Capitol police were investigating the discovery of at least three suspicious packages in Senate office buildings.

Senate Sergeant at Arms Terence Gainer said in an email that packages were dropped off at the offices of two senators, and Sen. Richard Shelby, R-Ala., said in a statement his office had received one of them.

A third package was found in an atrium on the first floor of one of the two buildings. A person who delivered at least two of the packages was being questioned, Gainer said, as Capitol police swiftly ramped up security.

Both the letters to Wicker, R-Miss., and to Obama were intercepted at off-site mail facilities.

Separately, Sen. Carl Levin of Mich., issued a statement saying an aide in his Saginaw, Mich., office had received a suspicious-looking letter. "The letter was not opened, and the staffer followed the proper protocols for the situation, including alerting the authorities, who are now investigating," the Michigan Democrat said in a statement.

The discoveries spread concern in the sprawling Capitol complex, and authorities swiftly stepped up their security presence.

In one case, police sealed off a hearing room where Defense Secretary Chuck Hagel and Gen. Martin Dempsey, the chairman of the Joint Chiefs of staff, were testifying.

In another, officers advised Sen. Joe Manchin and aides not to board an elevator because suspicious packages had been found on several floors of the Hart Office Building.

"They just told me there's something suspicious and they're looking into it," Manchin said. The FBI said the letters to Obama and Wicker were undergoing further testing. Preliminary testing can be unreliable, showing false positives for ricin.

Around the Capitol there was an increased police presence Wednesday. Outside, many public garbage cans were emptied and turned on their side. Yet public tours of the building continued as usual.

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FBI photo of a pressure cooker lid found near Boston bomb site.

Three days after the Boston Marathon bombing, investigators are still trying to unravel how a pair of blasts killed three and injured at least 170. On Tuesday, President Barack Obama called it an "act of terror," but said it is not clear whether the twin blasts were the work of a foreign or domestic group or a "malevolent individual."

As the country waits for answers about who the terrorist -- or terrorists -- is, the reality of how long that might take was discussed Tuesday on the PBS NewsHour. Michael Greenberger, director of the University of Maryland's Center for Health and Homeland Security, said he's optimistic that they'll find the perpetrator of the Boston marathon bombings eventually, but possibly not until evidence is painstakingly pored through and analyzed. "I have the unfortunate suspicion that this won't be solved quickly," he said in a story posted yesterday.

That made us wonder: how long does it take to catch a terrorist? To try to answer that, we compiled data on the most violent terrorist bombing attacks on the U.S. since 1974, and looked at how many days the manhunts took. We also wanted to know how long it took for the terrorist to be convicted and executed, if that's what their sentence called for.

The data is clear on one point: there is no answer, no template we can look at, to estimate how long this will take.

But as pointed out adnauseam, this is the first attack of it's kind to be captured in a social media world, where pictures and videos from professionals and amateurs are available in abundance. The FBI has released an image in hopes of uncovering clues to who was behind this attack.

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Watch Video Watch Visual Effects artist Joe Letteri explain how blockbuster hits used the science of light diffusion to make their digital characters more realistic.

It was near midnight in the winter of 1998 when computer graphics researcher Henrik Jensen made a discovery about light. While playing with a laser pointer, he noticed the way light seemed to diffuse through a sample of marble rock. It got him thinking about skin. Until then, digitally created characters in film had been lacking a certain human quality. And Jensen realized that graphic artists were failing to reproduce the way light rays pass through transparent objects, such as skin.

The phenomenon, known as subsurface scattering, explains why your hand has an orange glow when you hold it up to candlelight. The light passes through the skin and gets reflected out the other side.

Jensen teamed up with Joe Letteri, visual effects supervisor at Weta Digital, and they created the first digital character to have light-diffused skin: Gollum, the depraved human-like character in Peter Jackson's "Lord of the Rings: the Two Towers."

Gollum in Peter Jackson's Lord of the Rings: The Two Towers. Photo courtesy Weta Digital.

"It became obvious that one of the qualities in skin we recognize intuitively, and we don't think about articulating is the translucency." Letteri said.

This breakthrough won Letteri, Jensen and colleague Stephen Marschner the Sci-Tech Academy Award in 2004 for "their pioneering research in simulating subsurface scattering of light in translucent materials."

"The real excitement came when everyone got an eye full of Gollum and saw how convincing the skin texture was, even in close ups," said Bill Taylor, a member of the steering committee for the Sci-Tech Academy Awards.

The technique would later bring alive characters like the Na'vis, the 10-foot blue alien characters in "Avatar", King Kong in Peter Jackson's 2005 remake and Benjamin as an old man in "The Curious Case of Benjamin Button."

Since Weta Digital pioneered subsurface scattering, nearly every digital character has been aided by this technique, Letteri said. But despite its achievements, subsurface scattering is still evolving. Visual effects engineers and artists are working to master the close-up shot and find a so-called "unified model" for light movement -- a model that applies not only to skin, but to other translucent objects like hair, clouds and water.

Close-ups on digitally-created characters that reveal the flaws of the skin in fine wrinkles and pores also reveal the flaws of the technique. As the light bleeds through the skin, it also blurs the fine details.

"If you were really close up, you'd have to dial back to hold detail, Letteri said. "If you were far away, you would allow it to bleed a bit more so you got more of the translucency effect."

Neytiri, the Na'vi princess of the Omaticaya clan in James Cameron's Avatar. Photo courtesy Weta Digital.

Light diffuses differently through hair, clouds and water. And lacking a unified model, visual effects engineers have to create a new mathematical model for every single light source on every variation of material when digitally creating a scene.

"Skin has a complex substructure, so a unified model for light diffusion would capture the scattering that occurs at different scales within the skin, rather than treating it all as a homogenous medium," Letteri said.

A unified model, engineers say, will standardize the practice, simplify the math and improve the realism of the characters.

Letteri has improved this technique in subsequent films such as "King Kong", where subsurface scattering allowed for the softness around King Kong's eyes and in his hair, and in Avatar, where blue-skinned aliens had warm, human-like skin.

"We understand how to make things look good," Letteri said, "but we're really trying to understand the science behind it."

The first mathematical model for the technique was published by Jensen and Marschner in 2001. The path that light rays take through the flesh is not practically replicable for visual effects because it take a long time. So Jensen and Marshner came up with an approximation, finding a series of nearby points where the light will travel and affect the surface. Visual effects artists and engineers plot these likely points of travel for light rays at all points of the skin and for every frame. Then, the information is rendered digitally to create the effect.

"Once you present it, it's obvious, and you wonder how no one has thought of it before," Jensen said. "but it just wasn't on anyone's radar."

Technology is sometimes slow to catch up with the imagination of the screenwriter. James Cameron, for example, held onto the Avatar script for 10 years, because the technology wasn't advanced enough to do justice to his aliens. Letteri said, adding that he finally pulled it back out after seeing Gollum.

"It was the first time anyone simulated the real behavior of skin," Taylor said. "Rather than having an artist simulate skin texture and transparency through layers and layers of paint, they've recreated transparency. We can now make extraordinary characters believable."

Photo credit: Gollum from Peter Jackson's Lord of the Rings: The Two Towers. Photo courtesy Weta Digital.

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