they went out to give him his hug. he wound up losing his life. his sister lost her leg. the mother still in the hospital. this one family story, on the investigative side is a search for who did this and why continues. an apartment in revere, massachusetts, may be connected to the bombings. investigators leaving with bags of evidence, trace chemicals, maybe, hard drives, maybe, we're told. hopefully another piece in the puzzle of what happened here. >> grieving very much. that family in mourning, and investigators pounding the pavement right now. all around us, literally looking for any clue they might find from cell phone records to apartment buildings. all around the greater boston area this morning. >> we welcome our viewers in america, and around the world, to this special edition of "starting point." our continuing team coverage of these bombings. john and i here in boston. >> chris cuomo, john berman as you said. we are standing here this morning in downtown boston. we're about two blocks away right now. it's behind us on boylston street where these bombings took place. thousands of people are going about their work today. but it is not business as usual by any means. about 15 blocks of this downtown area shut down. a crime scene now patrols by national guards. this is what's happened since you went to sleep last night. we mentioned that 8-year-old richard martin among the three people killed. our boston affiliate whth reporting that his mother and 6-year-old sister also among those injured. as chris said the sister losing a leg. the mother having surgery overnight, possibly suffering a brain injury. another 144 are injured, including 17 people in critical condition. >> right. and we keep making that point. the bombs have gone off. but this situation is not over. there are people who are fighting very serious injuries. pictures we have not been showing you intentionally. this bomb was something right out of war. it was a low grade explosive. but it was throwing metal objects well over the speed of a bullet out of a gun. and when those things hit people, they change the way they look forever. people fighting in the hospitals right now to hold onto their lives and families trying to hold onto each other and make it through this as this city tries to recover and the rest of the country as it looks on. as those people are in the hospital, the investigators just as urgent. >> two tracks. there's recovery in the hospital. there's this investigation going on all around us. and overnight, authorities spent hours, hours searching an apartment building in revere, massachusetts. revere, massachusetts, about five miles north of boston. we don't know if any arrests were made in this case. what we do know is what we saw with our own eyes. investigators leaving with bags of evidence. >> they've got bombs that were exploded that can tell them the story. they say they know how they were detonated which is helpful. they say they have leads and they're making advancements on their investigation. and that is -- that is good for us to understand at this time. >> our pam brown is standing by outside this apartment building in revere, massachusetts. good morning, pam. what do you have out there? >> good morning to you, john. we're about 15 minutes away from downtown boston at an apament complex here on ocean avenue. this is where authorities spent eight hours yesterday executing a search warrant inside an apartment here, at this apartment complex. this is according to cnn's susan candiotti. local and state police, as well as firefighters, came in here yesterday, starting at around 5:00 p.m. again, here for eight hours. in an apartment on the fifth floor, we are told. we saw authorities bringing out boxes from that apartment. at one point, a state police officer brought in what looked like some sort of equipment, but right now authorities telling us that at this point, that no arrests have been made, that no one is in custody. we did speak to residents here at this apartment complex. they tell us that all they could really say was that there was just a lot of authorities here yesterday. that it's a bit of a scary situation for them to imagine that there might be a person of interest that was living here at this apartment complex. according to reports, the person that lived in the apartment that authorities were searching is a man of saudi descent who is here on a student visa. of course working to confirm all of this information with authorities. >> all right, pamela. thank you very much. certainly what may look like madness with all these agency people running around, we know very well, john, that joint terrorism task force they have a method to it. they're canvassing it. they say they have advances. we'll be hearing more information. this moves very rapidly these days. of course, as we say, two tracks. people still in the hospital. stories not over for families. very serious injuries that the medical staff here have done an amazing job. >> one of the silver linings of this attack, this awful event, is that it happened in boston, in some ways the medical capital of the world. so many great hospitals. so many great doctors here. and our poppy harlow is standing by at brigham and women's hospital right now. one of the best in the nation. and she has details on the more than 144 people injured in this horrible event. good morning, poppy. >> good morning, john. good morning, chris. and that number has held steady for, i can tell you, at least the past few hours since the very early morning hours. but it's the highest that we've had since this attack. 144 people. that is how many have been injured, all ranges of injuries from scratches and bruises to the most severe, complex, including amputations. we can also tell you that this hour that eight of those who are injured are children. and, of course, we told you extensively about that 8-year-old boy who lost his life. eight other children injured at this hour. 17 people in critical condition. 25 all severe -- their injuries are severe. they're in serious condition. ten people, we're told, had to undergo amputations. and late last night i was at a press conference at mass general, another key hospital here, and the doctor was as matter of fact as he could be saying look, this is our job, we are prepared for this. we never want something like this to happen, but we were prepared for a tragedy like this to happen. he called all of the patients brave. he basically said do whatever you have to do, and nay were very matter of fact. they weren't even talking about the trauma that they had just experienced. that is the way that one doctor described it. when you look at the age ranges of those injured, we're looking at someone as young as 2 years old, we're told by doctors, to some as old as into their early 70s. because, of course, many young spectators of this marathon and many more that were older that were running in this marathon were cheering others on. that's what we know at this hour. the doctors, some said yes they have seen injuries somewhat similar to this before. but they have never seen the quantity or the volume rush into the e.r. as quickly as possible. i also want to give our viewers some new information, john, coming from the boston globe this morning. according to a law enforcement official the "boston globe" is saying that 30 people were transferred after the attack to hospitals under a code red. that basically means with life-threatening injuries. so that law enforcement official telling the newspaper that could mean that the number of fatalities could rise. we are in the very early stages of knowing how these people will do, even after they get out of initial surgery. some, we're told, will have to go through multiple surgeries after that. >> poppy harlow. our thanks to you. those numbers that you bring up are what are so startling to so many people. one doctor overnight i heard say it was just depressing what he was seeing. another word you could perhaps use, chris, i suppose is infuriating. >> i'm sure. but the bottom line is no matter how he was feeling it's what these medical professionals were doing. if you're seeing pictures of what people were dealing with when those bombs went off you'd be amazed the death toll is not so much higher right now. no question phenomenal triage done. we showed you what's happening specifically with the investigation on the ground here. we know what's going on in the hospital. the overall architecture of this investigation very important. the team coverage is on that. national correspondent susan candiotti joining us this morning. what do we know at the latest, susan, in terms of how this investigation moves forward? >> hi, chris, and john. certainly we know that they'll be looking at all kinds of surveillance videos, they'll be checking into cell phone videos. and still photographs taken. obviously they are also in the throes of talking to all kinds of witnesses who might have seen something just before the two blasts went off and afterwards. and, of course, we're also looking at those devices. the two bombs that already blew up, and the unexploded devices. clearly there is a lot of ground to cover. the fbi is taking the lead in the investigation. >> it will do so through the boston joint terrorism task force. this will be a combined federal, state and local effort. it will be an ongoing investigation. it is a criminal investigation that is -- has the potential, is a potential terrorist investigation. >> reporter: and they're asking the public for help. >> anybody who has any information pertaining to this crime, to call -- >> reporter: so far no firm suspect in the bombings. but law enforcement sources say they have a number of active leads. they've issued a be on the lookout bulletin for someone described as a darker skinned or black male with a black backpack and black sweatshirt. that person could be a foreign national with an accent. sources say he tried to gain access to a restricted area before the blast. police are also looking for a penske truck that tried to gain access to a restricted area. a federal law enforcement official told cnn that both bombs were small. and initial tests show no c-4 or other high-grade explosive material. suggesting the packages used in the attack were code devices. still >> there's a certain level of sophistication. having made these bombs before, it's not easy. you just can't get it on the internet, make two of these bombs go off fairly closely together. so somebody had some experience. somebody practiced. >> reporter: sources tell cnn that one, possibly two, unexploded devices also were found. potential treasure troves of clues about who may have made the bombs. authorities still have no idea whether they -- this is either a domestic event, or a foreign-based event. i'm told that it's still too soon to know, either by the devices, and/or other information that they are gathering at this time. we can tell you this, there is a group called the pakistani taliban who are saying that they are not the ones who were responsible for this. however, that they support anyone who is attempting to kill americans. this is the same group, by the way, that claimed responsibility for the times square bombing back in 2010. you remember that involved a car bomb that sort of fizzled and they were able to catch that before it went off. back to you, chris and john. >> a claim of not responsibility this morning. susan candiotti our thanks to you. was it a domestic group, a foreign group? just one of the key questions everyone was asking this morning. there are many, many key questions out there. joining us is fran townsend, cnn's national security analyst and former assistant to george w. bush for homeland security and counterterrorism. also joining us, cnn analyst juliette kayyem who is a former assistant secretary for both u.s. homeland security and interestingly enough, a massachusetts homeland security adviser, as well. i want to start with juliette because we have some really is interesting information. new news about some developments going on at the airport right at this second. >> so, there's clearly going to be eyewitnesses. so what the police are doing is that they're starting to ask people at the airport to check their iphones. which is really smart. people don't know that they were witnesses. that they might actually have evidence in their phones or in their cameras. and so there's now sort of this search amongst all the people that were there, the tens of thousands of people, to say hey, did you see something? because the chances are, if the site was secure the last 48 hours, which it is because i used to do boston marathon security, someone probably got in in sort of chaos at the finish line. chaos is the wrong word. it's just more open than not. family members, reunification. that person may have been seen by others and there may be a picture of him or her or the people. so that's what they're looking for now. this is just grassroots investigation at this stage, without a big lead. >> fran, to bring you into the conversation, process of exclusion, not hearing the typical loud and proud we call it of a group taking responsibility for this. how does it allow the investigation to move forward? >> you know, chris, i think what we're seeing now is the fact that this -- the fbi as susan reported, want to be very deliberate as they walk forward and try to determine whether this is a foreign-based terrorist attack, or a domestic terrorist attack. you know, we reported last night that there was a saudi person in hospital with a leg injury. i spoke to a saudi official overnight. he said to me, in fact, there is a saudi female doctor in the hospital, with a leg wound, who is cooperating. the saudis have no reason to believe that this individual is a suspect in the bombing. and, in fact, when asked is -- was the search at the revere apartment related to this female saudi doctor, they couldn't say that. they said no, you know, we don't have any information on that at this time. so look as this unfolds we have to understand there will be people who are witnesses who cooperate, who are not related to the actions setting or making of the bombing that were set off at the end of the marathon. >> fran, you've been all over this story since the second it happened. i hope you were able to catch a little bit of sleep last night. some of the developments that did happen overnight was that search at the revere apartment. also this news from juliette that at the airport right now they're asking people to look at their iphones for any evidence, inadvertent evidence they might have. and also we now know there is a several block area behind us on boylston street that is shut down. it is a crime scene today. they don't want anyone going to work right there. based on these overnight develops, where do you see this investigation standing right now? >> you know, we read a lot into the fact that there were two devices that exploded, and one, or perhaps two unexploded devices used by law enforcement officials in boston. you know, remember, there was this case in times square with the unexploded van bomb. remember, these individuals, when they're going to set it off, forget whether it's foreign or domestic, it's redundancy. because one may not go off. so you want there to be multiples. it is possible that it's a lone wolf. it's not that difficult, we're told by law enforcement officials that these were small packages, these explosive devices. they had a horrible, tragic effect. but the fact is, it may not be a group. it could be an individual. and we have to let the investigators sort of work their way through this. i expect you're going to see breaks in the next 24 to 48 hours. >> fran townsend, thank you very much. we'll be coming back to you. appreciate you monitoring the situation as part of our team coverage. juliette, let me come back to you before we go to break here. let's deal with a little bit of the elephant in the room. president obama didn't use the word terrorism. became a little bit of a political football. but bottom line, forget about left versus right what are the practicalities about what language you use and how it may hinder or help going forward? >> what the president did not want to do is panic people before information was in. so that was a smart move not to use the "t" word, terrorism. but he also doesn't want to give a future defense attorney the ability to say, oh, well there wasn't a political motive with this guy. he was just some random -- >> political motive key to a finding of terrorism. >> so it's a nonstory. i don't know why people are raising it. everyone knows this was an act of terror. we should drop that. there's no brownie points to be gained at this stage. let's let the investigators figure out who did this and the response and life goes on. this seems to me just to be a very silly issue. >> don't handcuff yourself before you know what you're dealing with. >> exactly. we have no idea right now. >> all right, julia, thank you very much. >> up next we're going to take a look at the evidence left behind. so much to pore through right now. forensic teams are piecing together the tiny bits, the tiny pieces of the bomb. they're trying to find what we call the bombmaker's signature. we're going to go live to the pentagon with details just ahead. >> we'll be telling you things about this bomb we haven't heard before that are allowing this investigation to move forward. we'll be talking to people who are at the center of the investigation, the atf, the u.s. attorney in boston during 9/11. they will be joining us with the latest insights. >> i was over there like literally two minutes before i walked down and heard two big explosions. large plumes of dust, smoke, glast. everybody was going crazy. welcome back to this special edition of starting point, everyone. right now forensic experts are combing through evidence at the scene of the boston marathon bombing. it is just a few blocks behind us on boylston street directly back there. they're hoping to find the bombmaker's signature. from the maze of the explosives or perhaps from the unexploded explosives there. the joint terrorism task force is on board with long with a u.s. navy bomb detonation team. cnn's barbara starr is live at the pentagon with the details on this. good morning, barbara. >> good morning, john. we've talked so much about this notion of a bomb signature. what is it and why is it important? you know, bombmakers tend to put their bombs together the same way each and every time, and when they train others to put a bomb together that is the bombmakers signature. what experts are doing is looking at all the forensics. what material was used? how was it put together? what kind of detonator? what kind of fuse? what kind of explosives were used? how was the bomb placed, if you will? all of these things make up the signature. and there is a vast body of evidence over the years in iraq, in afghanistan, through terrorist attacks overseas, attacks here at home. the fbi, along with the military, has put together hundreds, if not thousands, of bombmakers signatures from material they've collected. so they're going to look at this scene and then see if it matches up in any way with something they already know about other incidents. they hope that this will be a valuable clue in leading them down the road. was it some type of foreign attack? was it a home grown terrorist? these are the kind of things they're looking at right now. john? >> and it's happening right on the ground, right behind us on boylston street. just one of the parts in the investigation unfolding this morning. barbara starr at the pentagon. our thanks to you. >> you know, in the investigative capacity, looking at what they know, the familiar, but dealing with this event, ye