0 responsible groups will feel the full weight of justice. >> the president saying we still do not know who did this or why and people shouldn't jump to conclusions before we have all the facts. that remains true at this moment as i speak to you. security has been stepped up around the white house this evening and passenger cities around the country from miami to new york city to los angeles. joining us from boston, katy turr. can you tell me the late nest boston in terms of where people are, what has been closed off and what the state of the city is now hours after the attack? >> it's very eerie here in boston. we're two blocks from the finish line, two blocks from where those explosions happened and pretty much nobody on the street. the police commissioner of the city asked that everybody stay inside, go back to the hotel rooms for their safety. there is a 15 block radius where you cannot get in with car traffic. so if you are coming in, you have to walk. off, people knew something was wrong. we're just a few steps away from where a woman stumbled away from the finish line with severe injuries. she had shrapnel injuries, that was involved in the explosions. she was take ton a local hospital. we don't know her condition. but with all those injuries, a lot of lower limb injuries, that's why there are so many people in critical condition. 100 injured, two people dead, and we have learned from a law enforcement source that one of the dead is an 8-year-old boy. the last thing they would expect today, a holiday, a celebratory day, they were not thinking that could have possibly happened. so you have a feeling of shock and a feeling of what could possibly happen next in boston tonight. >> katy, i feel like that was heightened partly because of reports subsequent of two explosive devices, abc news reported, others were found left behind. we have not confirmed if they were explosive. we do know out of precautionary measures, the boston police rendered themselves safe. do we know from the boston police whether they have secured afternoon area and are no longer concerned about the presence of secondary explosive dwoiss? >> reporter: we do not know that as of now. there will be a press conference in 30 minutes. we're expected to find out more. we know anything left on the ground, any package, as you can imagine, people are dropping things left and right. then the sploess, running away and dropping whatever is on them. treating everything as suspicion. we believe there was a potentially a third device, and safely detonated. a fire at the jfk lay briar, it's not clear what caused that. they say there were no explosions at the library. >> thank you so much. nbc news chief white house correspondent chuck todd joins us from washington. the president addressed the nation around 6:10. it was a fairly brief and very careful in terms of what the president said and what we know. what are you hearing from the white house now about what is unfolding since that address and why they took the approach they did? >> reporter: well, look, the issue, of course, when you say the approach, carefully chosen words, one of them had to do with why he didn't use the word terrorism. it was something that the white house themselves addressed quickly. you read the statement. aids debated whether the president should say is or not, and made the decision not to. one of the things you could hear it in his voice, talk to other officials, there isn't a lot of information. there's a bit of frustration, i think with law enforcement officialing from boston to washington about how little they seem to know at this point in time. now, i've talked to a couple of former white house security officials, one who said it's a loan wolf or a group they don't know anything about and didn't see -- see this group coming, if you will, because it's a group they hadn't been tracking, or they're just still trying to piece everything together. they may have something, but they want to be very, very careful, maybe overly careful because of what thing they night might know. >> that was quite evident in fact president's remarks. it seems when we use the word terrorism, we're talking about an action, but also a motivation. if there is no information now about who did this and who's responsible, as far as we know, no information, it seems to me prudent not to venture that word since that word does imply some specific ideological motivation in the act. >> reporter: i feel like i'm watching washington rush to say the words. and you're right, there is a technical definition, political motivation involved. and i think -- the president himself said we don't know the motive. they know it was somebody who committed an act of terror. >> right. >> reporter: and tried to harm and kill people, but don't know who it is and don't know the motivation. until they too do, that's why they're being careful. they know the president's words get parsed like nobody's business, so it wasn't as if this caught them by surprise. >> we just read recently a lesson for everyone, in the media as well in the wake of the benghazi attacks about how much initial reports may prove later to not be fully accurate. there's a lot of confusion in the aftermath of a chaotic event like this. >> reporter: and don't forget the atlanta ohms. that was a domestic terrorist who didn't take credit for it. there's the expectation, i think much of our security system is so focused on international terrorism sometimes, that i think that that's why, you know, that word gets thrown around. but, you know, there is -- there is assumptions, and i've heard others say, there's assumption somebody will take kred credit, that's the way it works internationally. we don't know. >> we've heard reports of expanded security around the white house, what can you dell us about that? >> reporter: we've seen it. they've gotten rid of -- pushed the perimeter to lafayette park, and pennsylvania salve closed to vehicle traffic, but now to tourist traffic. if you have an id badge, if you have business at the white house you can get in and out. but this is high tour season, so they're taking precaution and pushing everybody back. basically the opposite side of the street of the white house. >> nbc news chuck todd, thank you so much. appreciate it. >> reporter: you got it. >> i want to bring in ron allen joining us from mass general hospital in boston. the boston area home to an incredible number of some of the finest medical institutions in the entire country. what are you seeing hearing about those who have been brought there after the explosions today? >> reporter: absolutely right, chris. and all the doctors and medical staff in the town seem to be pulling together. people have come in from home to help out, because everybody was aware of what happened. first here outside the hospital, we were just told by the police some time ago to be careful about where we were, because there was an operation going on where there was concern where there might have been another explosive device. that threat, if there ever was one, as subsided, gone, so we are fine to stay here and broadcast. shopt just around the corner. i was able to have a conversation with an emergency room physician from beth israel, another hospital from across town, they received 20 to 30 patients. the doctor said there's an eerie calm because the crisis, the intense triage sessions have essentially ended. the situation is somewhat stabilized in the hospital. but there are at least seven patients in the operating rooms in surgery right now with life-threatening and what they describe as limb-threatening wounds. a lot of people facing partial amputations or total amputations of arms and legs. as you might expect where there's a situation where a bomb goes off, a lot of shrapnel and moving around and flying around at a violent pace, and that's the kind of injury they're seeing that's causing the most life-threatening injuries. he said that there are also -- i asked him about what kind of shrapnel, he said it looked like -- he's not an expert, something of an expert, bb gun pell lets. it wasn't the kind that was glass and other kinds of debris that you would a bomb exploding in the city street. exactly. he describes something like a bb pellet, which is something, the investigation will determine this as we go on, something that might have been packed into an explosive. that's one thing the police and investigates are trying determine, what they were made of. but that doctor mentioned that which i thought was interesting. a lot of tension here in the city. i just flew in and drove through the city, i know boston well, i used to live here, it's eerie where people are walking around trying to get a sense of where things are going, what's happening. desperate for information, hanging on the latest word about what's going on, what's new. there are a lot of police road blocks around boston. hard to get around. the traffic is very thick. just as we were pulling up, there was a warning from some of the police. but the investigation 69 parking garage, area has passed. but it's an example that the whole situation is still evolving, continuing. it's not over. of course, for people -- the patients in the hospital, i count seven at beth israel, a handful here. i'm not sure of the exact numbers because it's a fluid situation. but there is still the possibility of people fighting for their lives, trying to deal with potentially life threatening, and as i said before, what they're describing as limb threatening wounds. >> our latest reporting is 113 total injured. i'd like to play sound for you. dr. al stir from mass general addressed the media. take a listen. >> some of the patients have already received traumatic amputations at the scene, their legs have been blown off, and bleeding profusely. so in conjunction with those right on the scene, they've managed to stop the bleeding, but they're in the operating room already. >> my yes question there in boston is this, we've seen in other emergencies and crisis, caused by natural disasters or other, million infrastructure overwhelmed by the sheer number of people. it seems from the reporting today that the medical infrastructure, the first responders, emt all the way into the trauma centers have been able to accommodate the incredible scale of this, of the violence that happened there today. >> reporter: yes, i don't get the impression from talking to medical personnel or the reports that the system is overwhelmed. i don't get that sense at all. you'll recall that, again, right at the end of the marathon, just past the finish line, there's a triage center set up, medical tents set up to hands injured runners pushing themselves across the finish line. those areas were overwhelmed by people running in after the bomb blast. it's fortunate, if we can use that word that it happened four hours plus into the race, didn't happen as the leaders were crossing the finish line, because there would have been many, many more thousands more people, runners and spectators in the area. that is one thing that's kept the number of casualties down. but i don't get any sense that the medical facilities are overwhelmed. they are amongst the best in the country, in the world. they know what they're doing. as i've said earlier, i've heard a lot of volunteers have come rushing in who weren't on duty to be here to help out. as i'm standing here talking to you, i can still hear the sound of blangss around the city heading this way, and there's an ambulance going by just up the street there. so, again, this is still a very fluid situation. i've heard the number of 130 injured, the question now is how many have been treated and released. we don't have a clear number on that. but we do know there are perhaps a dozen or more people,ing? in that range, based on the reporting, of people in potentially life threatening situations. not critical, not giving out that much information, but there's still a lot of people in severe dangers. >> ron allen, thank you so much. one of the things striking about what we know so far is the ratio of pfatalities to casualties. two people lost their lives, but it's good that so many appear to have avoided death. and right now joining me is donald, former fbi essential agent who investigated the oklahoma city bombing, the u.s. embassy attacks and be the usa coal in 2000. thanks for being here. the thing everyone wants know is who did this. >> of course. >> it's the thing everyone wants to know, but we cannot answer that, so instead, as someone who has transported into the aftermath of a mass casualty event in the role of investigator, explain to us what is happening now. who is showing up in boston under who's direction, who is coordinating and what are the processes undertake ton find out who did this? >> it's going to be a long night and week for the agents and the joint terrorism task force in boston. what typically happens, and i'm positive what's happening now, first thing is they have a joint command post set up. it'll be a jop, a joint operations center. this was more than likely already set up to handle an event like this because they were dealing with the boston marathon, a special event. >> standard procedure. >> resources in place which saved them a lot of time. it's tough when you have a cold start, a bomb goes off, you have to set it up without any kind of prewarning. so they've got that infrastructure in place. and in that will be representatives from all of the agencies that are basically involved in the investigation, state, local, federal, there will be people coming in from washington. and this will be the nerve center of the investigation. so right now, it's kind of in 14/7 mode. >> and what agencies are represented ? when you talk about this, who is part of that? >> i can't tell you everybody in boston, certainly the fbi, the state police, atf, all the federal agencies, local police. i was in charge of the international terrorism division in new york as my last job. so new york, for example, over 50 participating agencies in the joint terrorism task force. so certainly there are a lot of resources that will be traugt brought to bear on this situation. >> what do those resources do? what's the checklist? where do you figure this out? >> the first thing is that we've got some good forensic evidence that's been collected. number one, the teams are going to go out and try to put these devices together that exploded. they're going to collect any little bits and pieces, wire anything that can help put the devices together. and try to figure out, you know, what did it look like before it blew up? but, we've got a break in the situation in that there were other devices, as i understand it, other devices retrieved that law enforcement rendered safe. so we have some unexploded devices that could possibly really provide significant leads. for example, do all devices -- are they similar? does it look like they were made bit same person? a lot of times people that make bombs make them the same way. they have a pattern, a signature. sometimes there's fingerprints, dna. you can look at components of the device and figure out where they came from. backtracking, you know, records. many times that the explosive material itself carries a signature, so they can tell the manufacturer who made it. if it was high order, low order, gun powder, what was the signature of this? >> let me ask you this. based on the -- are think conclusions to be drawn about the sophistication or capacity to produce the kind of bombs based on how fatal they appear to have been? is there anything we can conclude based on who would have the ability to make a bomb that would have this kind of effect? >> well, for example, if it's a kind of a pipe bomb that's made with black pouder and a timing device, and as we saw in the early reporting, shrapnel, bbs, whatever. that's a device that's not overly complicated to make. >> and that would expand the circle of plausible suspects because that is a capacity that many people have. >> less technical, the easier it is for the average person to get their hands on this. as opposed to some of the devices that we've seen coming out of the afghanistan and pakistan that are made by more sophisticated bombers and techniques, for example, where they use tatp as the explosive. this was the device that was attempted to be used in the new york subway. this takes a higher degree of train. it's also a lot more lethal. my opinion, and this is just opinion, i am not a bomb tech, but if we had seen devices that were more sophisticated, i think we would see a lot more casualties and it would have been a lot worse. >> and a more narrow sense of possible -- >> possible, but that's -- that's only based on the video and just kind of in my amateur assessment. >> let me ask you this other question, and we have an eyewitness who was in the medic tent today when the explosion went off that i want to bring in, before we do that, what is the rule of law that currently operates guiding the investigators? i think this is an important question. it's contested in the aftermath of the underwear bomber on christmas who's custody he was taken into. when we are talking about the joint operation center and investigations happening across a number of agencies, what rule of law controls? >> the fbi is in charge of terrorism. so it is in the -- it will be an fbi-led investigation. >> which means the united states constitution and the due process it affords and all of the do thing is and crossing ts that goes along with that. >> that goes along with that. however, that is not to say that intelligence collection isn't a big part of this. and the -- the trick is to find that delicate balance. so, for example, if there is information to be collected by intelligence means, whether it's a sensitive source, domestic, overseas, we're going to pursue that -- every angle of that. if it means that somebody's in custody, and the decision is made that we to want interview this person without reading may ran da rights -- >> in foreign custody? >> in u.s. custody there are situations now where a lot of people are saying you don't need to read the miranda rights right away. if is strong suspect is picked up, or could provide significant information, i think that addition could be discussed between doj, fbi, the white house -- >> presumably as the fbi is going through this, they are looking to make sure no secondary attacks is the first priority, and then to make sure they maintain the possibility of getting ultimately a criminal conviction. >> absolutely. >> joining us now is an eyewitness, greg, ran the marathon and was in the medical tent with the explosions happened. he joins us by phone from boston. greg, zwrieb describe what you were doing in the medical tent at what time and what the scene there was like. >> yeah, the first thing to share, this was wave three, so i was a charity runner for the alzheim alzheimer's association. we started at 10:40 a.m., and i finished my first under four. hi pushed pretty hard in mile 25 and 26, what that means i was winded and dizzy, i was ready to faint. as i crossed the finish line one i asked for medical assistance, a wheelchair, i heard your reporter say, typical post marathon, to give, if you will, a little tlc. i'm near mass general myself, another ambulance. i was in the tent, i think it was approximately eight minutes after i had crossed. so close to 2:40 p.m. that i heard an explosion, i was laying on a cot, getting my blood pressure taken, my initial question, was that thunder? it was a beautiful day in boston. i didn't think that was the case. pretty loud crack, ka-boom. you could sense in the tent that it was more than thunder and a very serious situation. >> did you hear the second explosion right afterwards? >> i think that's what triggered it, you knew then -