Heavily armed FBI and police SWAT teams combed through Watertown, Mass. in a massive manhunt for Boston Marathon bombing suspect Dzhokhar Tsarnaev. Video: YouTube/Scott Sassone, YouTube/David Tamang.
Authorities said they captured the 19-year-old suspect in the deadly marathon bombings late Friday after one of the biggest manhunts in U.S. history paralyzed an entire metropolis.

Police and Federal Bureau of Investigation agents converged on a house in the Boston suburb of Watertown late Friday, and took into custody Dzhokhar Tsarnaev, one of two brothers alleged to have exploded two homemade bombs in downtown Boston, killing three people and injuring more than 175.

Residents who have been on edge and trapped inside of their homes all day burst into applause upon hearing the news. As police pulled away from the scene where Mr. Tsarnaev had been trapped and surrounded by law enforcement for hours scores people lined the street clapping and screaming.

"We are so happy, we are relieved," said Ashot Davtian. "I feel bad for the people who lost their lives but I am happy it's over."

Authorities had halted public transportation, closed schools and advised residents to stay locked indoors for much of Friday during the manhunt.

Mr. Tsarnaev had escaped capture after leaving behind his older brother, 26-year-old Tamerlan Tsarnaev, who was killed in a firefight with police early Friday. The brothers, carrying an arsenal of explosives, fired guns and threw pipe bombs in the fight after an overnight crime spree that left dead an officer of the Massachusetts Institute of Technology, authorities said.

The violence began late Thursday when the two men, recorded on a security camera at a 7-Eleven store in Cambridge, allegedly went to the campus and shot the officer, then used a gun to steal a Mercedes sport-utility vehicle, briefly kidnapping the driver.

The driver was released and his tip drew police on a chase that ended in the shootout in Watertown, Mass.

The two brothers, who lived in Cambridge, Mass., had escaped notice for three days after Monday's bombings. Late Thursday, the Federal Bureau of Investigation released pictures and videos taken from security cameras near the marathon's finish line.

The broad release of the images apparently triggered a chaotic getaway attempt by the brothers, who arrived separately in the U.S., one around 2002 and the other in 2003 or 2004.

"Releasing that video really expedited things. People actually did recognize them," said Rep. Michael McCaul (R., Texas), chairman of the House Homeland Security Committee. "That moved things along more quickly, to the point they decided they had to get out of town."

For most of the day, Boston was virtually shut down as authorities conducted the search. Public transit, including commuter rail, buses and subways, were halted and Amtrak closed service to and from the city. Schools and offices also were closed.

Armed personnel carriers rumbled down city streets and rifle-wielding police officers knocked on doors.

On Friday evening, officials said they were lifting the request for people in some areas to stay indoors, and were restarting the mass transit system.

Chalena Graustuck, 23, who lives a few blocks from the brothers' home, said she felt trapped: "It's just scary. I don't feel safe at all. I want to get on a plane and go far away from Cambridge but now we're stuck here."

Authorities gave no indication of what motivated the brothers. Their family roots stretch to the rough-and-tumble Russian republic of Chechnya, which has been a wellspring of terrorism over the years.

"We believe this to be a terrorist," said Boston Police Chief Ed Davis. "We believe this to be a man who's come here to kill people. We need to get him in custody."

The FBI had interviewed Tamerlan Tsarnaev in 2011 at the request of the Russian government, but it found no suspicious evidence and closed the matter, a U.S. official said.

Friends said the two brothers, especially Dzhokhar, had settled comfortably into U.S. society. He was enrolled at the University of Massachusetts Dartmouth.

After Monday's attack, the brothers apparently stayed around the neighborhood where they had settled after immigrating, authorities said.

On Tuesday, Dzhokhar came to an auto-body shop to pick up a Mercedes he had dropped off for repairs, said Gilberto Junior, who works at the shop.

The younger brother was jittery, said Mr. Junior. "He was biting his nails and when he was talking to me his legs were like this," Mr. Junior said, shaking one leg. "He said, 'I need the car now. I need the car right now.' "

At 5:20 p.m. Thursday, the FBI released the photos and video of the brothers.

Investigators said the two men apparently decided they needed a car to flee. It wasn't clear why they didn't use the Mercedes from Mr. Junior's shop.

At 10:30 p.m., MIT police officer Sean Collier, 26 years old, was ambushed and fatally shot in his car.

Massachusetts State Police officials at first thought the shooting was unrelated to the marathon bombings.

At MIT, police used flashlights and search dogs to search the campus for more than an hour, with officers circling parts of the campus and clearing away passersby.

Then the officers ran into their cars and sped away.

Many headed to Watertown, a Boston suburb. The brothers released the driver of the stolen Mercedes after forcing him to withdraw cash from an automated teller machine.

The brothers told the man, who wasn't identified, that they were responsible for the marathon bombings and then let him free, officials said.

The driver notified police, who spotted the stolen Mercedes and began the chase.

Authorities believed they had trapped the car in a densely populated residential neighborhood of Watertown. But the brothers put up a fight.

"They were wearing suicide vests, they were throwing the pipe bombs out to get rid of their evidence," said Mr. McCaul, the House lawmaker.

Tamerlan Tsarnaev got out of the car and was shot, authorities said.

Richard Donohue Jr., a police officer, was seriously wounded in the firefight.

Massachusetts police said Dzhokhar Tsarnaev fled on foot. His brother, Tamerlan, was brought to a hospital and pronounced dead around 1:30 a.m.

Neighbors reported powerful explosions and many gunshots as hundreds of police swarmed the neighborhood. Helicopters flew overhead.

Adonis Karageorgis, a 35-year-old dental student, said he saw the sky light up from his apartment. "You could just smell the smoke," he said. "It went high in the sky."

Friday's manhunt began first in Watertown, as police dashed down streets with police dogs, flashing lights, searching backyards and knocking on front doors.

Police early Friday confirmed the brothers were also suspected of killing the MIT police officer. By 5 a.m., the news was out that one brother was dead and the other was in hiding.

Officials expressed fears the brothers could have accomplices, one reason that authorities called for the broad shutdown of universities and offices in the Boston metropolitan area.

Later Friday, they said it appeared the brothers were acting alone.

Rep. Peter King (R., N.Y.), who sits on the House homeland security and intelligence committees, said he hoped the fugitive was captured peacefully.

"I'm hoping they get the second guy alive and can interrogate him, so we can figure out, did they do it on their own or are they affiliated with a larger group?" he said.