Massive manhunt for the two most wanted man in America has come to a dramatic end. There was a collective sigh of relief and cheering and streets. Okay. Tonight one alleged bomber captured the other... See More
Massive manhunt for the two most wanted man in America has come to a dramatic end. There was a collective sigh of relief and cheering and streets. Okay. Tonight one alleged bomber captured the other dead. All day until just a few hours ago this city was in an unprecedented. Locked down with nearly a million people. Warned to remain inside their homes -- colleague Lindsey Davis watched the whole search unfold from the streets of Watertown. Boston it was under siege today as authorities -- Hunted and killed two camera -- are nine -- 26 year old suspect in the marathon bombings and ultimately. Captured his younger brother nineteen year old Joseph -- after an intense standoff which he -- inside a boat in the backyard of the Watertown resident. Today we are -- the public's help elect the frantic search for the suspected Boston Marathon bombers began Thursday when the FBI released these grainy images. Our first glimpse of the most wanted man in America. The FBI needed the public's help tracking down their -- suspects in the attack but they warned then that these men were armed. And very dangerous. No one should attempt to -- apprehend them except law enforcement do not take any action on your home. It was no exaggeration. Late last night authorities discovered MIT police officer Sean collier. Shot and killed by the suspects. At first authorities didn't realize there was a connection to the bombings. Then authorities say the two men carjacked a Mercedes SUV in Cambridge. Briefly kidnap the driver and led police on a wild violent chase through the streets of neighboring Watertown. Then a dramatic shootout. You made an automatic prior. In all 200 rounds were fired between the police in the suspect's. We'll also reportedly threw explosives from their car in the exchange to the gunfire we believe that one of the suspects. Was struck. And ultimately taken into custody and the camera -- are nine and it was critically injured during the firefight and taken to a nearby hospital where he eventually died. We spent about 1015 minutes trying to resuscitate this patient. But he is alleged accomplice was still on the loose an army of police descended on the neighborhood. -- as a quarter of mount Auburn in Kimball. Less than half a mile away from where that shoot -- took place police officers. Are seeing that they're gonna continue to go door to door. By now a more complete picture of just how violent and heavily armed the Brothers -- began to emerge. In Watertown authorities owners evidence of homemade bombs and pipe bombs -- -- pressure cooker and possibly similar to the one used in the bombings. We believe this to be a terrorist we believe this to be a man who distributed kill people. We need to get him in custody by. Early morning subways and buses were suspended soon after schools and universities closed down. Police alerted residents to stay indoors and quote shelter in place this is a very serious situation that we're dealing with. Swat teams descended upon a home -- Norfolk street in Cambridge searching for the suspect. Soon after Massachusetts Governor Deval Patrick ordered all of Boston and the surrounding areas -- To go on lockdown. They're asking people to stay indoors. With the doors unlocked and gotten to open the door for anyone other than any probably identify and law enforcement officer. Our number one priority right now is with these neighborhoods here in Watertown. And making them safe in finding this individual. Acquaintances in the Boston community immediately recognized -- -- -- And voiced utter shock they say he was a well liked hard working honor student who lived in the US for many years. It's just absolutely shocking and horrifying for all of us it's. It just it seems like a nightmare week it's hard to believe that that someone that you know was so friendly and funny just a couple years ago could have done these kinds of things. By mid morning the father of the two suspects who lives in Russia spoke to ABC news is beyond -- creative via telephone. He denied his son's involvement and said they refrain -- made a plea for his sons to surrender peacefully adding if he is killed all hell will break loose. He could not. Say enough how innocent how kind. His sons both our -- continue to speak -- treated throughout the day. He said surrender I want you to come home alive -- a bright future ahead of you. At midday the lockdown still in full force. Residents on edge peeked out windows prisoners in their own homes our doors are locked up our windows shades drawn it's just. You know really desolate and keep the doors locked in battle in the relentless there -- is a uniformed. Identified law enforcement officer on the other side and people now being told that they may have to stay in their homes for through the weekend. By afternoon the FBI removed a computer hard drive from the home of his sister and after a full day chase authorities lifted the lockdown. And none of those leads have been truthful extend a break in the case. Gunfire by the waters damaged but we're talking about dozens of rounds fired. A lot of residents out on the street crowning -- street right now they started cheering. And -- -- -- rushing back into the perimeter here people were yelling go get them eyewitness George diseases told ABC news his neighbor went to check on his -- today. He saw blood. Climbed up a letter to open the cover over the boat. It looked at the boat and there was something he's moved the -- -- -- some things we're interaction that's -- strengths -- he went in his direction. Any you don't get -- that that was a -- Within the hour officers sweep the area and finally news the suspect is taken into custody. Reportedly found alive. -- -- -- -- And you know prosecute and and bring to justice. Mayor Tom Menino tweeting simply we got it surrounding neighborhood cheers of USA USA broke out. Law enforcement simply took office. We are -- eternally grateful for the outcome here tonight we have a suspect because -- We're exhausted folks but we have a a victory here tonight. -- let's not forget those people along the way. As the night drew to a close the president addressed a grateful nation all always been tough week. But we've seen the character of our country wants more. Tonight Joseph hearts are nine and is in serious condition at Beth Israel Medical Center being treated for his injuries. And the city can finally sleep. For Nightline I'm Lindsey Davis in Watertown Massachusetts.
This transcript has been automatically generated and may not be 100% accurate.