>> reporter: well, we're still waiting for an update, richard. we were told yesterday there were eight people in critical condition in surgery, and they would be going through multiple surgeries during the next few days as they try to recover. let me show you the front of the hospital because there's something new down there. there's a heavy police presence as you can perhaps see. the officers in those bright green coats. there's also a national guard -- national guardsman there and a couple police cars. they're talking to everybody who's coming in the hospital. there's also, we understand, police in the hospitals around town trying to question people as witnesses as they try to figure out what happened. you see this scene all over boston, especially in the 15 or so square blocks of the back bay where the explosion happened. the area is completely locked down. a lot of businesses are closed. people are having difficulty getting in and out who live there. we were staying at a hotel in the area. and you needed identification to get in and out. so again, a lot of heavy security like you see here. patients at the hospitals, some in critical condition, still undergoing surgery. so there is the possibility that

the death toll here could rise, but at this point, it's still stable at three. richard? >> ron allen live from boston, thank you so much for that report. flags are flying at half-staff in washington today as lawmakers on capitol hill amend their schedules in response to what some call an act of terror. today intelligence committee members will be briefed by homeland security and the fbi on the boston bombing. nb krshs's tracie potts is in washington with more for us. tracie, good morning to you. >> reporter: richard, capitol police are telling visitors here expect more officers in the public areas today. some lawmakers have already been briefed. others get an update on this investigation today. >> the house will now observe a moment of silence in memory of the victims of today's attack in boston. >> reporter: congress observing a moment of silence for boston's victims. this morning the capitol flag remains at half-staff. later today, the fbi, homeland security and intelligence officials brief lawmakers on what they know about the explosions.

>> the most important thing is we do it right. we get the right information. >> reporter: lawmakers were quick to call it an act of terror, but the president specifically did not. he sent an fbi team to boston, promising justice. >> we will find out who did this, and we will hold them accountable. >> reporter: there's a security perimeter around the white house and more security throughout the city this morning at airports and metro stations. but d.c. officials say the parade, concert and fireworks for today's emancipation day celebration will go on. >> i want people to feel comfortable and take public transportation, come down to the event and enjoy yourself. we feel very comfortable. >> reporter: d.c. on high alert as washington tries to pin down the nature of the attack. also from washington, the irs is telling boston area taxpayers, boston only, don't worry if you missed the tax filing deadline last night. they'll give extensions, and they plan to talk more about how that will be done later today. richard? >> traci potts, thank you so much. people at the scene of the

explosions are speaking about what they saw. one witness saying he could feel the explosions from his feet to his chest. a photographer on the scene shared his story with our own brian williams. he was just half a block away when he heard the first explosion. >> it was one of the craziest scenes i've ever scene. everyone was rushing. no one knew what to do. most of the people were running away. you know, the ems was running towards the scene. nobody knew what to do or what was happening. everyone was just in fear. >> this is like a bomb explosion that we hear about in the news in baghdad or israel or some other tragic place in the world. >> it went off and me and him -- we're rooting on our friend and like oh, yeah. and then it was, like, boom! both of us, we've been to afghanistan. you expect that there. i didn't expect that here. everyone started screaming and running towards us. i was, like, dude, what's going on? we jumped over the railing and

ran down there. >> first explosion happened a block further down from us and the second one was right across the street from us. yeah, it was loud. it was really, really loud and people just -- chaos every where. >> i mean, there was just families all around us with kids, yelling and screaming. we just wanted to try and get away as quick as possible. >> again, eyewitness accounts speaking with our own brian williams. coming up, you may be waking up to a heightened state of security where you live. why so many cities across the country are stepping up protections. you're watching a special edition of "early today."

in the wake of the boston bombings, federal investigators are on the ground now combing through evidence to learn more about the explosive devices and ultimately who is behind this attack.

joining me now is former fbi profiler and nbc analyst clint van zant. good morning to you. the question might be what's the next committee step in this investigation? >> well, the investigators have got a lot going for them, richard, as far as forensic evidence and otherwise. as you know, law enforcement sources suggested at least two unexploded devices have been found. that's magic for investigators right now. notwithstanding forensic evidence, fingerprints, dna, hairs, fibers. they'll also see how the device was built. they'll be able to see what the components are. they'll be able to trace those components back. we're told that these are relatively unsophisticated low-order explosive devices. richard, that's something like if we think back to the olympic park bombing in 1996. >> right. >> those pipe bombs filled with black powder with shrapnel in or packed around them. that's the type of device.

and realize in this case, where a bullet, let's say, for example, moves at about 1,000 feet a second. that low-order explosive, when it went off, it would still be pushing those bbs and ball bearings and other shrapnel at about. 000 foot a square second. so investigators are trying to gather all of that information up as well as looking at photographs, do interviews, surveillance cameras. they have a lot to do. but they have a lot to work with. >> so those bombs having a unique fingerprint on top of that showing all the video. we've got the video, we've got the still photography, we also have sound. how important will these thousands of hours be to this investigation of that sort of media out there? >> well, it has to be. and one of the things that is going to take time notwithstanding reviewing the surveillance cameras that are set up in the location, hundreds and hundreds, probably thousands, of people were taking pictures with iphones and

snapshot cameras all morning long up to and including the time of the blast. all of that film needs to be recovered and reviewed by law enforcement. we know there were two explosive devices about the length of a football field apart. so we need to show pictures. if we can't show obviously somebody putting both devices down, we need photographs showing who was at one area? who was at the other? who disappeared very quickly? that is all going to help law enforcement as they try to put these blown-up pieces together to give us a face and a motive for a killer. >> all right. a giant puzzle pieces they're trying to put together at the moment. clint van zandt, thank you so much. nervous investors looking for fallout. the selloff continuing overseas this morning. weak chinese economic data sparked monday's fall. and later the bombings in boston drove up investors' fears. police and military presence

ramp up at travel hubs in major cities. in boston, governor deval patrick saying the city is open, but it will not be business as usual there. and thanks to marathon runners who ran straight to the city's hospitals and donated blood, massachusetts general met all of its blood needs yesterday. however, they are encouraging more donations beginning at 7:30 a.m. eastern this morning. "early today health" is brought to you by vagisil ph balance wash. after the break, more on the attack at the boston marathon including what authorities can do to help keep us safe at major public gatherings. this is "early today."

in the wake of the boston bombings federal investigators are on the ground combing through evidence to learn more about the explosive devices and ultimately who is behind this attack. what we do know is terrorism experts have been warning on an attack like this for years. one on a so-called soft target that's difficult to protect. "dateline's" chris hansen has more on the investigation. >> reporter: in the immediate aftermath of the explosion police are searching for the answer to the obvious question, who is responsible? this from the boston police commissioner. >> if anybody knows of any

information that could lead to the arrest or prosecution of the individuals responsible for this, they should call us. >> reporter: according to law enforcement sources, there were two bombs possibly in backpacks which were also loaded with metal objects designed to kill and maim. at first the police commissioner reported another bomb had exploded at the jfk library. >> the third one occurred at jfk about a half hour ago. but it turned out to be an unrelated fire. according to intelligence sources there was no online chatter previous to the bombings. >> we have no information that this was going to happen. >> reporter: a white house official called the bombing an act of terrorism. here's what counterterrorism experts are telling us is likely happening in the investigation right now. surveillance video from the numerous cameras in the area is being downloaded and reviewed. and the bomb material that was recovered is being carefully gathered and undergoing forensic analysis. but there's something else that

will no doubt need to be investigated in the days ahead. how was someone able to plant and detonate explosive devices with all those surveillance cameras, thousands of eyewitnesses and plenty of law enforcement? this man says it's easier than you might think. >> in an open society like the united states, we are vulnerable. >> reporter: sean henry is the former executive assistant director of the fbi and is now president of a cyber security company called crowd strike. he says the boston marathon is an event that experts call a soft target. >> it would appear this particular type of event would be considered a soft target comparatively speaking to an airport or a major government building because of how large it is and how many people would attend, it would certainly be more difficult to protect than a building or something of that nature. >> that was nbc's chris hansen reporting. reaction to monday's bombing has spread well beyond our borders and created a heightened state of alert around the globe.

more on that for you. plus the very latest on the investigation into this act of terror. we'll be right back.

as the investigation continues into yesterday's tragedy in boston, the fallout is being felt around the world. for details, we go to annabel roberts in london. annabel, good morning. >> reporter: good morning,

richa richard. not surprisingly, this tragic event is front-page news here. this is the big spanish newspaper with a picture on its front page. "the irish times" has another image of people being treated in the immediate moments after the event and the "daily mail" has the headline "bloodbath at the marathon." "the daily telegraph" also. attention is turning to the london marathon due to take place on sunday. it will go ahead. a government minister has said the best way to show solidarity with boston is for the event to go ahead as planned. however, security is being reviewed. the organizers say they cannot be complacent. now, like boston, hundreds of thousands of people turn out to line the route. it is a big family day out. the route passes all of london's major landmarks. there are, of course, about 36,000 runners taking part. so it's a huge event. the risk level in the city is already classified as substantial.

but officials point to their success policing big sporting events like last summer's olympics, saying they have got plenty of experience. back to you, richard. >> annabel roberts, thank you. an update out of boston in just a moment. first let's shift to weather and bill karins. as we've been talking about, critical steps in the investigation in the outdoor venue there in boston. how's it look? >> they were fortunate yesterday because they had the sunshine. they had the mild conditions. it wasn't too windy out there. it hasn't rained since then. it's not going to. no problems collecting all the evidence and everything else that they're going to need for the investigation. but as far as people getting out their doors and getting on with your day today, we aren't looking at anything troublesome in the west. it's still a little chilly and cool. beyond that we're doing okay. all the horrible weather is stuck in northern colorado and wyoming with a big old snowstorm for late in the season. you notice the temperatures are chilly everywhere in the west. but look how cold it is in the rockies still from denver northward. still in the 20s. still feels like the middle of winter. in the west, should be a dry

day. we should be looking nice in arizona. los angeles should be pretty good, too. as i mentioned, it only gets better from here. look at l.a. by the time we get to friday, we could be into the low 80s. a significant warm-up is in the cards for many areas of california and all the way up into the pacific northwest. that's a look at your natio san jose, 67. and even arizona, a little cool by your standards. have a safe quiet weather in the days ahead. >> bill karins, thank you so much. i'm richard lui, and this is "early today," just your first stop of the day today on your nbc station.

terror at the boston marathon. this is what we know right now for you. three people were killed in two explosions which happened at 2:50 eastern time monday afternoon. the twin blasts occurred as little as 12 seconds apart near the finish line of the race. one of those killed was an 8-year-old boy. more than 140 others were injured including some who lost limbs. officials say there were two confirmed explosive devices both of which contained bbs or ball

bearings. the fbi has taken over as the lead agency on the massive investigation. police issued alerts for a man seen leaving the scene and looking for a rental truck. seen attempting to enter the area near the finish line. anyone with information is being asked to call 1-800-call-fbi. authorities questioned one person at brigham and women's hospital. but the police commissioner said he was not a suspect and no one is in custody. an official also saying here law enforcement conducted a search related to the incident at an apartment building on revere beach parkway. a white house official said the investigation will treat this as an act of terror. president obama saying "we'll find out who did this and hold them accountable." flags were lowered to half-staff in d.c. and around the nation as the country mourns with boston. at least one powerful image in this morning's papers is capturing the human toll of the attacks at the finish line. two men tending to a bloodied

woman laying on the ground on boylston street. "the boston globe" calling it "marathon terror." "new york times," the paper's subheadlines calling it "panic at the finish line." "usa today," "terror returns." showing police officers rushing to the aid of an injured runner in the street. time now for a look ahead. there will be an update on the boston marathon bombings at 9:30 eastern this morning, and the boston celtics game against indiana has been cancelled and will not be rescheduled. coming up later this morning on a special edition of the "today" matt lauer and lester holt are live in boston with all the late-breaking details on yesterday's deadly explosions. hear from a doctor who jumped in to help the wounded while waiting for his wife to cross the finish line. now keep it right here for more news, weather and sports. i'm richard lui. thanks for watching this special edition of "early today," just your first stop of the day today on your nbc station.

have a good one.

. . as soon as that second one went off, it was complete mayhem at that moment. >> it is a criminal investigation that has the potential, is a potential terrorist investigation. >> we will find out who did this and we will hold them accountable. >> we are going to get through this. we will get through it together. looking live at san francisco.

flags across the country at half-staff today. a sombre reminder of the terror at the boston marathon, less than 24 hours ago. good morning to you. i'm laura garcia cannon. i'm jon kelley. a terrifying scene out there. more than 100 were hurt. at least 17 remain in critical condition. we have learned overnight, police searching a home in suburban boston as part of this investigation. so far, no arrests. >> at least three people, including 8-year-old martin richard, died in the attack. this is a picture of the youngest victim just into our newsroom. at least one person from the bay area right here who was hurt in that blast. a young boy from martinez. "today in the bay's" chris pallone is in boston with the overnight developments on what appears to be a well-coordinated attack. >> reporter: a little more than four hours into the 117th boston marathon, the race came to a chaotic and violent end. two explosions near the finish

line about 12 seconds and 100 yards apart shattered windows and sent runners, spectators and officials scrambling for safety. >> people were running, sprinting back. the runners were going the other way. there were people running, crying. >> reporter: dozens of the wounded were rushed to several boston hospitals. among the dead, an eight-year-old boy. doctors say they are treating wounds from the blast impact and flying debris. in an instant, they went from treating dehydration and blisters to things you would see on a battlefield. >> a variety of injuries. probably the most common injuries are combined lower extremity injuries. combined meaning bone injuries, soft tissue injuries and vascular injuries for the lower extremities. >> reporter: the fbi is leading the investigation. evidence collection teams have been brought in from new york. at the white house, president obama vowed it will be a swift and thorough search for whomever planted the devices.