Captured! Second Boston Bomb Suspect Arrested

Updated at 6 p.m. Friday:

Cheering residents lined the streets of Watertown, Mass., late Friday after police captured the final suspect in the Boston Marathon bombing.

The arrest followed a two-hour standoff in which authorities cornered the 19-year-old suspect in a backyard boat and used flash-bang grenades and tear gas to flush him out, according to Watertown Patch and CNN.

The drama began shortly before 4 p.m. with bursts of automatic gunfire, followed by police cars, SWAT vehicles and ambulances racing to the scene, sirens wailing, CNN said.

WBZ news radio said a police helicopter used thermal imaging to help pinpoint the suspect.

After the arrest, a little boy tossed a Red Sox cap into the air and one woman shared cookies with reporters, according to tweets posted by the Boston Globe, which said alleged bomber Dzhokhar Tsarnaev was "alive, conscious, captured."

Authorities later said Tsarnaev was bleeding heavily and in serious condition.

Original story:

Boston went on lockdown Friday after chaotic gunfights overnight killed one bombing suspect and one police officer, and prompted a massive manhunt for the second suspect.

News reports identified the surviving suspect as Dzhokhar A. Tsarnaev, 19, of Cambridge, an immigrant from Chechnya. His 26-year-old brother, Tamerlan, was killed in a shootout with police.

As the manhunt continued, the suspect's uncle pleaded for him to surrender, according to the Los Angeles Times.

“You have put shame on this family and on the entire ethnicity” of Chechen, the uncle, Ruslan Tsarni, told reporters. “Turn yourself in.”

However, the suspects' father said his sons were framed.

“I will never believe my boys could have done such a terrible thing,” he told ABC News. “I have no doubt they were set up ... because my sons are Muslims.”

Meanwhile, Boston authorities swarmed through Watertown, Mass., searching for the remaining suspect, who they believe may have been wounded in the shootout.

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

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The violence began Thursday night with the fatal shooting of an MIT campus police officer, then a carjacking by the suspects. That led to a chase in which the suspects allegedly tossed five pipe bombs and a grenade at police before engaging in a shootout in Watertown early Friday, according to CNN. Tamerlan Tsarnaev was pronounced dead at a hospital after the gunfire and Dzhokhar escaped on foot, reportedly after driving over his brother.

A gruesome photo of the dead suspect, naked and bloody on a slab, was later circulated among Boston law officers, some of whom found it cathartic, according to the Boston Globe.

CNN said authorities found more homemade explosives at the scene of the shootout, including a vest worn by Tamerlan.

News reports said the Boston area was placed on virtual lockdown so police could eliminate any civilian movement in the streets while the search continued. The Red Sox and Bruins canceled their Friday night games. And the city's transit system was shut down til about 6 p.m. Eastern time.

Meanwhile, in Southern California, law enforcement officials planned to be on heightened alert this weekend at a series of outdoor events, including the Long Beach Grand Prix, an autism walk outside the Rose Bowl and the L.A. Times Festival of Books at USC.

"We are encouraging everyone to go about their business as usual," Los Angeles police Officer Sally Madera said.

Local authorities said they had received no credible threats, but would deploy extra personnel -- including undercover officers -- as a precaution in areas where large crowds were expected.

Clarification: An earlier version of this story said the violence began with the robbery of a 7-Eleven in Cambridge, Mass. Police said Friday the suspects didn't hold up the store, but coincidentally were there around the same time.

-- Watertown Patch and City News Service contributed to this story.