that michelle obama is she'lling the real bomber of the boston marathon because it was an inside job like 9/11. there's always going to be a very, very, very exciting market for these things. when a political party sees profit, when a political party decides to seek political advantage by trafficking and courting it and popularizing it, that is a different thing and i am not sure we know how that ends. that does it for us tonight. we'll see you again monday night. now it's time for the premiere of "caught on camera: terror in boston." please have a great weekend. the camera captures the last seconds of normalcy. then shows everything, changing in an instant. >> i saw the amount of blood, the injured and the bodies just like a war zone. >> we've had an attack.

>> reporter: lives lost. >> i can't believe this is happening. this doesn't make any sense. >> reporter: and lives saved. >> i was carrying somebody who lost both of their legs. in the explosion. >> we will go to the end of the earth to identify the subject or subjects who are responsible for this despicable crime. >> reporter: the investigation goes digital as a massive manhunt is crowd sourced. >> we quickly secured a warehoused aan undisclosed location and technicians began to work on digital evidence from video and photographs. >> reporter: images discovered. and then revealed to turn up the heat on the suspects. >> as soon as these guys knew that everybody in the world now was looking for them, then it was game on. >> reporter: cameras record the crime. the carnage, the clues. and the conclusion. >> subject is in custody. again, is he in custody at this

time. >> we're exhausted, folks. but we have a victory here tonight. >> if the goal was to terrorize the city, it was a success. if the goal was to defeat the city, it was a failure. >> reporter: a celebratory moment is shattered in a flash. an explosion near the finish line of the boston marathon. then, 13 seconds later, about a block away, another.

as the scene unfolds, hundreds of cameras are pointed at the chaos and destruction. >> as soon as an incident happens, many, many people start taking out their cell phones and you can see sometimes with one cell phone you could see the other person who's filming with another cell phone. so it's not difficult to figure out what they captured, where they captured and you have it immediately. >> reporter: on the morning of the 2013 boston marathon, the 50 degree weather is perfect for running. this proud tradition, more than a century old, is held every year on patriots day in massachusetts, the third monday in april. the first race had just 15 runners. today there are more than 23,000. they start in waves, 9:30 a.m., the elite women. 10:00 a.m., elite men.

a third group takes off at 10:20. followed by a fourth and final wave at 10:40. the elite winners come in about noon. over the next several hours, the rest of the runners expect to come in at their own pace. ing abouting about -- "boston globe" senior sports reporting is recording near the finish line. >> they're trying to beat the four-hour mark, not the elite runners but are good runners. >> reporter: a "boston globe" photographer has covered the gruelling 26.2-mile marathon for 20 years. >> the race was as usual, got a little boring. the kenyans are going to win it again. there was nothing special. >> reporter: david able is there, too, a "globe" staff writer on sabbatical for the year to study filmmaking at harvard. >> i was standing on the finish line at the center because i was

making a video of the first drafsh dwarf to run the boston marathon. she was due in in five minutes. >> 27,000 strong. >> reporter: another video, shot by one of the hundreds of spectators in the crowd captures an ordinary race with typical announcer play by play. there's absolutely no indication of the chaos and devastation just seconds away. >> that's the only marathon in the world other than the olympic marathon that that was the case. at 2:50 p.m., 4 hours, 9 minutes and 53 seconds after the final runners head out, this turns into a lead story. >> cannon salute, musket fire

going off to salute certain runners coming across. my first reaction was maybe something terribly went wrong with some equipment or, you know, we have manhole cover explosions in boston. >> reporter: silva's video camera and the still camera capture what quickly becomes an iconic moment, a 78-year-old runner named bill ifrig thrown to the crowd by the force of the the explosion. >> i didn't know he was blown over by the blast. it was so intense at that moment, so confusing and then the three police officers came running towards me, one had their service revolver drawn. i never realized she had her gun out until i looked at the images when i got back to editing. >> reporter: just as the shock of the first blast sets in, 13 seconds later, there's another, about 100 yards away.

>> i was holding a video camera and so for me, i knew that my role there was to document what was happening. >> i looked over the barricade through my camera and realized it was really bad. i mean, i didn't know at that point but when i saw what i saw, i saw bodies on top of bodies. i saw pools of blood. i saw people with their legs missing. >> when i got up to the sidewalk and saw the amount of blood and the injured and the bodies just like a war zone or just like it was a steven spielberg movie. >> we've had an attack. >> reporter: within hours, silva's gripping footage is on the air. >> oh, my god. oh, my god. oh, my god. >> reporter: the second blast

goes off just outside the forum restaurant on boylston street. without hesitation, employees spring into action to help the injured. five of them spoke to rock center's harry smith. >> there were members of our staff that were right there, holding on to people. taking their belts off to stop, you know, bleeding and different things like that. >> reporter: bartender julie weeden, back to visit friends at her old job just for the day ends up helping her friend heather, who's been badly injured in the blast. >> all of it is so traumatic but to have somebody you know -- >> yes. >> have a friend of yours. >> uh-huh. >> almost have her -- >> you feel guilty. >> you feel guilt? >> uh-huh. >> i just think that people were

trying to help other people. strangers did not think about themselves. >> look [ bleep ]. >> reporter: in the first chaotic minutes, it's not confirmed what caused the explosions. spectators don't know it yet but they're about to become key eyewitnesses. >> is it safe to be here? >> probably not. >> reporter: their photos and video men the to celebrate joyful moments are now potential evidence caught on camera. but how will investigators find answers within the hundreds of hours of videotape and possibly thousands of stills? ♪

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>> something just blew up. >> reporter: it's mayhem after two explosions go off within seconds of each other at the 2013 boston marathon. hundreds of cameras catch a horrific scene. "boston globe" photographer john temackey says he instantly knows he's documenting history, snapping these images, despite the danger. >> they said you have to get out of here, there may be another explosion. i kept on shooting, running to the blast scene an i saw what i photographed. it wasn't something, you know, i wish anybody would ever see. >> reporter: at first glance, the whole scene is a snapshot. representing the worst of humanity, but as the smoke clears a few minutes later, beyond the destruction we can

also see the best of humanity. carlos arredondo, the man in the cowboy hat, captured in this striking image is one of many who disregards his personal safety and runs toward the carnage to help. >> you're hurt, you're carovere in blood. >> i was carrying someone who lost both legs. >> reporter: he came to the race to honor his sons. carlos shows unbelievable courage, tearing through a fence to get to the injured. and immediately tending to this man, jeff bouman, who had both legs blown off. arredondo leaves bouman as he's loaded into an ambulance.

>> i was carrying this flag and i just -- my instinct was to go help him and see what i can do. just pray for the angels. >> reporter: it's still only minutes after the blasts, photographer john temackey finds other people, just like carlos arredondo aiding the wounded and snaps a series of unforgettable images, this one of a man applyiapply ing tourniquets to a woman. >> and another, this teenager laying on the ground, giving help to total strangers. >> reporter: he doesn't know it but the two victims in the photos he takes are mother and daughter. celeste and sydney corcoran and the man helping celeste is her husband, kevin. the family is there waiting for

celeste's sister carmen to cross the finish line. >> i have a vivid memory of seeing my daughter and my friends being blown back, falling backwards. my daughter's arms outstretched like this and falling backwards. and nobody was standing up anymore in front of me. so for a couple of seconds, i just looked left and right and then looked down and there she was, my wife celeste. i saw her eyes were open. i know she's alive and then i start looking around and there are limbs everywhere and blood and i look down at her body to see if she's okay and i notice her legs. when i saw that, instinct takes over. you take your belt off, put a tourniquet on, yell to a guy who happened to be running towards me. he gave me his belt. i put on another one and laid down next to her. and just told her i loved her and that everything would be okay and i just kissed her face

and just gently caressed her while people were trying to get to us. >> reporter: by the time kevin turns around, his daughter sydney isn't there. >> i just entrusted to humanity and that had to be somebody out there that was taking care of her. >> reporter: turns out someone is looking out for kevin's daughter. one of the people hovering over sydney in this picture is matt smith, a total stranger who rushes to her side. while kevin doesn't know anything about his daughter's fate, he hurries to the hospital with his wife celeste whose injuries are so severe, doctors need to amputate both legs below the knees. an hour after the explosions, the family discovers sydney is being treated in the same hospital as her mom. about the time officials confirm the cause of the devastation, small homemade bombs. it's not until kevin speaks to the surgeon that he realizes how

seriously his daughter is injured. >> so i ask him in no uncertain terms, i needed to know just myself, what's your opinion, how bad was this? and he said this was a mortal wound. and if the people did not get to her when they did, she would have bled to death. >> those people saved her life. >> i'll never forget those words. >> reporter: matt smith who helped save sydney's life, visits her in the hospital. >> i spoke with him first and thanked him. we both cried together. you couldn't meet a nicer guy. i just got so lucky that these people were actually in the area and did what they did. >> reporter: just before 9:00 p.m., officials confirm three deaths from the bombings. 23-year-old boston university grad student lingzi lu. a boy, 8-year-old martin richard and a 29-year-old named krystle

campbell whose mother patty is shattered. >> couldn't ask for a better daughter. i can't believe this has happened. she was such a hard worker at everything she did. this just doesn't make any sense. >> reporter: as friends, family and neighbors grieve on the evening of monday, april 15th, the scale of the suffering is becoming clearer. 144 people lay wounded in beds scattered across five boston hospitals. 24 in critical condition. >> i saw humanity at its best. i saw heroism, i saw compassion. i am so proud of all those people. i mean, i think what i recorded in photos i have are testament to that. >> reporter: but urgent questions remain unanswered. who could have done this? and more immediately, is it over?

>> i'm not prepared to say that we are at ease at this point in time. >> reporter: investigators have a mountain of video and pictures to scour, with no time to spare. the intense search for the killers. [ male announcer ] you are a business pro. governor of getting it done. you know how to dance... with a deadline. and you...rent from national. because only national lets you choose any car in the aisle... and go. you can even take a full-size or above, and still pay the mid-size price. this is awesome. [ male announcer ] yes, it is, business pro. yes, it is. go national. go like a pro.

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>> reporter: the boston marathon bombing is one of the most photographed attacks in american history. >> there were cameras everywhere. television reporters everywhere. there were citizen journalists everywhere. >> reporter: the images captured at the race become the cornerstone of the investigation. >> within 15 minutes we were already obtaining video up and down the marathon route and in the general vicinity. >> even as we were removing victims yesterday, officers were assigned to go into the local establishments and secure those videos. >> it was immediately clear the fbi was going to lead the way on this. the agents flocked in from all over the country, bomb

technicians, evidence collection experts. and this became what very quickly was described as the biggest criminal investigation in the history of boston. >> reporter: as photos and videos continue to accumulate, dozens of investigators analysis ima -- analyze image from before, during and after the explosions. >> we quickly secured a warehouse at an undisclosed location and technicians began to work on digital evidence from video and photographs that came in as well as processing bloody clothing and scraps of the bomb. >> reporter: officials are inundated with images. still, at a tuesday morning news conference, they make a plea to the public for more. >> there has to be hundreds if not thousands of photographs or videos or observations that were made at the finish line yesterday. they're sitting out there amongst everyone that's watching this event this morning. and i would encourage you to

bring forward anything. >> somebody had a photograph. accidentally taken or deliberately taken, of the people who left those bombs there. and law enforcement wanted those pictures. >> reporter: police even take the highly unusual step of stopping travelers at logan airport in boston to check for potential clues on their cameras. later tuesday morning, president obama addresses the nation. >> this was a heinous and cowardly act. and given what we now know about what took place, the fbi is investigating it as an act of terrorism. >> we saw downtown just a tremendous number of agents in white suits, methodically moving through streets, up on roofs, looking for the tiniest little bits of physical evidence. >> reporter: as investigators sweep the vast crime scene, doctors recover evidence from victims in the operating room.

>> small metallic fragments that entered their body, shrapnel, nails, that these bombs had. >> reporter: on tuesday afternoon, 26 hours after the attack, news organizations obtained photos of forensic evidence related to the blasts. >> among items partially recovered are pieces of black nylon which could be from a backpack and what appear to be fragments of bbs and nails, possibly contained in a pressure cooker device. >> what was immediately clear, these were homemade bombs. they were made locally. you can't transport them very far. you make them, put them together, put in the detonator and you use them. >> reporter: it's apparent the explosives are designed to maim and kill. >> at this time, the there are no claims of responsibility. the range of suspects and motives remains wide open. >> reporter: tuesday evening with the bombers still at large, hundreds gather on boston common

at a candle light vigil to honor the victims. >> there was a certain amount of dread about when are we going to find these people? who are they? what would motivate someone to do this. >> reporter: unknown to the public, the fbi determines through surveillance video that a young man in a white baseball cap displays suspicious behavior amid the chaos at the crime scene. in addition, according to bloomberg news, at boston medical center, a potentially critical lead. jeff bouman awakens from a double lower leg amputation and asks for a pen. he scribbles these words. bag, saw the guy, looked right at me. when fbi agents interview him, he reportedly describes a man with a black cap and sunglasses dropping a backpack on the ground and walking away just before it explodes. bouman's tip helps investigators zero in on who else to look for

in all the images. >> they did try to use facial recognition software. once they had this picture but to make it really work you have to have a clear front-on picture of someone to match against databases. >> reporter: without a positive i.d., the fbi is faced with a pivotal decision. should it release the photos and solicit the help of the public. >> we don't know who they are. we don't know if they have other attacks planned. every hour we wait they're potentially getting further away. >> reporter: it's a call that could backfire. >> if you publicize their pictures, it gives them a pretty clear signal that you know at least what they look like and it's going to encourage them to flee and flee faster. >> reporter: but it could help stop the flood of misinformation being circulated by virtual vigilantes who are identifying potential suspects and publishing their own theories. >> there was a lot of bad information out there and some lives have been damaged by it. and you can't take it back.

you can't apologize but you can't take it back. >> reporter: on thursday, april 18th at 5:20 p.m., the fbi releases images of the two men it believes are responsible for the attack. suspect number one, and suspect number two. >> we consider them to be armed and extremely dangerous. >> they had run out basically all their leads and that was the final moment they decided to release the pictures on thursday night. >> reporter: once again, officials appeal to the public for help. >> in an instant these images will be delivered directly into the hands millions around the world. we know the public will play a critical role in identifying and locating these individuals. >> as soon as these guys knew that everybody in the world now is looking for them, then it was game on. copd makes it hard to breathe...

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the surviving boston marathon bombing suspect was

moved earlier to a prison facility. he's at the devens federal medical center which houses inmates who need medical care. president obama addressed concerns about syria today. he said there are questions about how, when and where the assad regime may have used chemical weapons. and the house voted on a bill to end the furlough of traffic controllers. back to "terror in boston." >> reporter: just three days after the bombings that ripped through the boston marathon, the first pictures of the suspects are revealed to the public. grainy images captured by security cameras. >> today we are listing the public's help to identify the two suspects. >> reporter: one of the many calls to the fbi comes from david green, a runner in the marathon who had snapped this

single photograph. nothing in the image stood out to him before but after the photos of the suspects are released, a friend sees something that astounds him. >> when they released that video image, my friend told me, look at the bottom left-hand corner. when i did that, i realized there was something there. >> reporter: that something is suspect number two. blending into the chaotic scene. >> and i called the fbi, got through to an agent and he immediately escalated it. >> reporter: green had captured the clearest image of suspect two that investigators had seen. >> you can clearly see what he was wearing. you could also see clearly see the bomb was not on his back anymore. >> reporter: on thursday evening with the fbi's encouragement, green begins circulating the photo on facebook. >> when we got that picture and it went out to the public, it really ramped things up. now people weren't looking at a grainy image. they had something they could

look at closely. >> as soon as these guys knew that everybody in the world now was looking for them, then it was game on. >> you've cornered a wounded animal now type of thing. it adds to the level of danger. >> reporter: shortly after 10:00 a.m., more violence, shots ring out at m.i.t. in cambridge. 26-year-old campus police officer sean collier is shot and killed while sitting in his vehicle. there is speculation that the incident is connected to the bombers but no one knows for sure. >> routine call of a disturbance. he's responding, gets there and within seconds he's shot in the back of the head twice, execution style. he had no chance to defend himself. >> reporter: for officers, there's no time to reflect on the loss. within minutes, they receive a report of an armed carjacking of a black mercedes suv in another part of cambridge. the victim who does not want to be identified, would later tell police that he was held at

gunpoint by two men. >> according to this owner of the car, he escaped. he claims that they told him they were the boston marathon bombers, that they shot a campus policeman but they were not going to kill him because he was not an american. >> reporter: some of the suspects' movements during the carjacking are caught on camera. suspect number two is seen here on this atm's security cam. >> they did take the victim's atm card and went to an atm machine and withdrew $800. >> reporter: suspect number two is later seen on a security camera at this shell gas station. it's here that the carjacking victim escapes unhurt but he leaves one thing behind. >> we got notified that the victim's cell phone was left in the carjacking vehicle. so the cambridge police were actually able to ping the phone and pick up where its location was. >> reporter: it leads them to watertown, massachusetts. just after midnight, police

intercept the suspects who the world will soon learn are brothers. a gun battle erupts in the middle of a residential street. more police officers and fbi rush to the scene. people watching from their homes capture it all on camera. and upload their video to youtube. >> [ bleep ]. >> shooting right in front of my house. >> [ bleep ]. >> reporter: roommates andrew kitzenberg and christian watch anxiously from their windows. >> i had my iphone right at the bottom of the window. >> reporter: just outside the suspects are taking cover behind their vehicle. >> i was tweeting an uploading a lot of the photos i had. >> reporter: positioned closer to police officers, michael is shocked to see what's happening outside his front door.

>> that's when i turned my camera on and i started filming it. then it was pop, pop, pop, pop. and then pop, pop, pop back. and then it was just like a shootout, like a movie. before you know it, there's at least 30 to 40 cars just lined up. >> is this related to the terrorists? >> reporter: but the suspects arsenal isn't limited to bullets. they unleash explosives. >> the explosives brought it to a whole other level. i saw a metal device from the images that i saw earlier in the week that resembled the pressure cooker bomb. after they threw the explosives, it shook my room. it left a marking in the middle of the street. >> reporter: suspect number one makes a define the move. >> he started running down the street charging and still engaging in gunfire, guns ablazing. >> he took on one of our

officers and got within ten feet of exchanging gunfire back and forth. then he ran out of ammunition, thank god. one of our officers was able to come out and tackle him in the street. all of a sudden one of them looks up and yells, get out of the way. >> the second shooter got into the suv and that's when he turned around and started driving. >> you heard the mercedes roar. just like someone trying to gun it. >> they jumped out of the way, barely got out of the way. one brother ran over the other brother and dragged him down the street in the suv for a short distance. >> right when he crossed the intersection they unleashed. no exaggeration, it had to be 100, 200 bullets or maybe more, then he was gone. >> after everything calmed down, i saw a bullet hole in my wall. it had gone right through the chair. a few minutes ago i had been sitting directly right there. >> reporter: during the

firefight, one officer is critically injured, 33-year-old richard donahue is rushed to the hospital for emergency surgery. suspect number one is taken to another hospital where attempts to save his life are unsuccessful. >> i'm not sure if he would have survived if his brother didn't run him over but he certainly -- we knew he was hit. multiple times but certainly there was no chance once his brother ran him over and dragged him down the street. >> reporter: as dusk turns to dawn, the world learns that the suspects in the marathon bombings are responsible for the violence overnight and that suspect number two is now on the run. >> we believe this to be a terrorist. >> reporter: the police pursuit is about to become one of the biggest manhunts in u.s. history. [ clang ] my house is where plants came to die. but, it turns out all i was missing was miracle-gro potting mix.

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>> reporter: friday, april 19th, after a deadly shootout with the suspects, authorities reveal the names of the men whose faceses are now infamous. 26-year-old tamerlan tsarnaev killed overnight. and his 19-year-old brother, dzhokhar, who is on the run in an already terrorized city and considered armed and extremely dangerous. >> indications are strong that the current outstanding party may be wearing a suicide vest. >> i need to be clear about this, this situation is grave. we are here to protect public safely in these neighborhoods in watertown right now. >> reporter: 8:00 a.m., in an unprecedented move, authorities order all residents of boston and surrounding towns, including watertown, to stay in their homes. >> they didn't know where the suspect was. they had no idea. they say to themselves, they still have explosives. they have guns. >> you don't want these guys running around and potentially

taking a hostage. the safest place for the residents of boston and the surrounding area was in their homes. >> reporter: boston looks like a ghost town. despite the lockdown, news crews spread throughout the city, risking their lives to bring a transfixed nation any news of the manhunt. >> let's go to carrie sanders on the ground. what can you tell us. >> i'm not exactly sure. the officers are yelling get down, get down. some people are now getting back up. >> i've been in war zones, iraq, afghanistan and lebanon. so it was about as weird as it can get to think that i'm in an american city and this is happening. >> reporter: as blackhawk choppers hover overhead, police go door to door in an attempt to smoke out the suspect. trapped inside their homes, instructed only to open their doors for identified police,

frightened bostonians record their city under siege. >> actually look out the window and notice there are nine s.w.a.t. guys about to kick down the neighbor's basement door. i just snapped a picture of that. kept on posting a bunch of them and had lots and lots of messages where people said, keep it up. you're my news for today. >> everybody in their own sense became a reporter of what was unfolding. >> reporter: in maryland, media gather around the suspect's uncle who demands his nephew give himself up. >> i say, dzhokhar, if you're alive, turn yourself in! and ask for forgiveness. >> reporter: 6:00 p.m., he's still at large. but city officials announce the major threat is over. and they're lifting the lockdown. >> the stay indoors request is lifted. remember, there is still a very, very dangerous individual at large.

>> in the final analysis, everyone agreed that it was the right thing to do. >> reporter: lifting the lockdown becomes key to finding the fugitive. >> david hennenbury goes out to smoke a cigarette, looks at the boat in his backyard. something doesn't look right. >> he takes a stepladder, jumps up into the cockpit, sticks his head under the tarp and sees an immediate pool of blood, calls 911. they were within foot distance. they immediately evacuate my mother and my stepfather david. >> reporter: again, a camera provides critical information. thermal imaging gives a birds eye view of what appears to be the suspect in the boat. >> we had a helicopter in the sky that was able to tell us there was a body in there, that based on heat seeking they could tell it was a human body and they could tell us it was

moving. we knew he was alive and they had a threat. police rapidly clear residents from the area and the situation escalates quickly. >> we heard a barrage of gunfire. >> reporter: news cameras are too far away to capture what's unfolding but neighbors aiming cell phones out their windows record an explosion of gunfire. >> [ bleep ]. [ gunfire ] >> [ bleep ]. >> [ bleep ]. >> maybe 40 police cars sprinted down our street and there were all sorts of law enforcement running towards this house with their guns pointed. >> reporter: in the air, the same infrared camera that revealed the suspect in the boat captures video of the operation, while the audio plays out over the police scanner. >> we have a person in the boat who's trying to poke a hole

through the boat. >> when they finally discover he's in the boat, they didn't simply go in to kill him. they went in to try to get him out. they're very concerned who's doing that. here's a man who set off two bombs, who's been responsible for killing one policeman and gravely wounding another. they were very worried about the safety of their own o officers and people in the surrounding areas. >> no one is to fire their weapon. repeat, no one is to fire their weapon. >> reporter: fearing the suspect may be strapped with explosives they send an armored vehicle with a robotic arm to approach the boat. >> we are going to get guys up here on the third floor. >> reporter: the robotic arm tears away the cover, revealing tsarnaev curled up on the floor with no vest of explosives. officers throw flash bang grenades at the boat where the suspect is lying motionless. suddenly after the third flash -- >> we have movement in the boat.

he just sat up. he's moving, flailing about, quite a bit of movement. >> reporter: fbi negotiators attempt to get him out of the boat. and then law enforcement moves in. >> when we first started moving up to the boat he was laying on the side of the boat. he was in and out of consciousness. when we got 10 to 15 yards from him, he sat back up, we moved from behind the shield cover, pulled him down and put the cuffs on him. >> reporter: 8:45 p.m., while the anxious city waits on edge for news, massachusetts state police snap the image the world has been waiting for all day. >> the subject is in custody. again, he is in custody. >> reporter: new details emerge. >> they wanted to continue to keep killing. pacino ] the inchd are everywhere around us. every minute. every second -- we fight for that inch. ♪

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>> reporter: friday evening, april 19th. the hunt is over. after alluding a massive dragnet that shut down greater boston, bombing suspect dzhokhar tsarnaev is captured. the 19-year-old is wounded but alive. >> the first thing they did was dress his wounds, put in an i.v. and establish an airway. >> they had to get him to the hospital, make sure he would live because ultimately they wanted to get more information from him. >> reporter: tsarnaev is rushed to the hospital with gunshot wounds to his head, land and throat. as news of the capture spreads, crowds erupt in spontaneous celebration and gratitude. >> it's just an amazing ending to a horrible week, horrible day. >> ten minutes ago. it was a war zone. now everyone is out here clapping. unbelievable. >> we're exhausted, folks but we have a victory here tonight. >> reporter: at beth israel deaconess hospital where several victims of the bombings are

recovering, tsarnaev is in serious but stable condition. >> he suffered a wound to the throat. agents already know that communicating with him would be somewhat difficult. >> reporter: though tsarnaev can't yet speak, federal interrogators are anxious for answers. >> number one, why? number two, did you have any help? because the concern here is were these two lone wolves or were they working with others? >> reporter: according to u.s. officials briefed on the investigation, the terror suspect cooperates with interrogators from his hospital bed, using pen and paper and nodding yes or no. they say that tsarnaev admits he and his older brother tamerlan carried out the bombings that killed three and injured more than 260. >> u.s. officials say that he told them what motivated him and his brother was the wars, the american wars in afghanistan and iraq. >> reporter: they disclose the younger tsarnaev insists the

ethnically chechen brothers acted alone without direction or assistance from any foreign terror group. >> government officials reported that he learned to make the bombs from al qaeda's online "inspire" magazine. >> reporter: dzhokhar tsarnaev is charged with multiple federal counts, including the use of a weapon of mass destruction. he became a u.s. citizen in 2012. on capitol hill, some demand he be treated as an enemy combatant but the plan is for him to be tried in a civilian court. >> under u.s. law, the united states citizens cannot be tried in military commissions. >> reporter: of the two brothers, tamerlan tsarnaev is believed to be the driving force behind the bombings. >> from all indications, he's the one that encouraged his younger brother to participate. >> reporter: tamerlan tsarnaev was a lawful, permanent resident of the u.s. and married with a young daughter. but family members say he had changed in recent years.

embracing an extreme interpretation of islam. >> wasn't working, living at home, sort of a stay-at-home dad. was increasingly anti-social. >> he had that youtube account that posted clearly jihadi videos. >> reporter: tsarnaev spent the first half of 2012 where he lived as a teen, in dagestan, a volatile region in russia that borders chechnya. >> there's a lot of people speculating that at a minimum he met with people involved in this chechen terrorist group and possibly and likely received some training. >> reporter: authorities believe the brothers had every intention of continuing their alleged jihad after the marathon bombings. >> we learned through the joint terrorist task force that the boston marathon bombers had plan to travel to manhunt to detonate the remaining bombs in times square.

>> reporter: but they never made it, thanks in part to a public armed with digital cameras. >> uniformed officers asking people do you have a pictur were you there that day? >> reporter: from the initial bombings to dzhokhar tsarnaev's dramatic arrest, cameras were there. 102 horrific hours that left 4 innocent people dead and altered the lives of hundreds more forever. >> we won't ever get a satisfying answer of why somebody puts bombs at the boston marathon and kills people. there's just no explanation for it. >> if the goal was to terrorize the city, it was a success. if the goal was to defeat the city, it was a failure. >> we also send our prayers to the collier family who grieve the loss of their son and brother, sean. >> our prayers are with the campbell family of medford,

their daughter krystle was always smiling. she would have turned 30 next month. our prayers are with the lu family of china who sent their daughter lingzi to bu so she could experience all that this city has to offer. and our hearts are broken for 8-year-old martin with his big smile and bright eyes. they set out to intimidate us, terrorize us, well, it should be pretty clear by now they picked the wrong city to do it. not here in boston. not here in boston.

due to mature subject matter, viewer discretion is advised. >> put your handses up. >> i guess the worst part about gangs is paranoia. it's like a virs, it invades. former gang members attempt to leave deadly rivalries behind. but for some, the past is anything but resolved. >> i don't think no one could ever take this p