- Less than an hour after authorities lifted the shelter-in-place order for Boston-area residents, a barrage of gunfire was heard on a street in Watertown, Mass. where police had been hunting all day for the surviving suspect believed to be responsible for the Boston Marathon bombings.
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The Boston Globe reported that Suspect 2, Dzhokhar Tsarnaev, 19, was cornered.
There are reports that a person was spotted in a boat in a backyard in the area but it's not clear if that is the suspect.
Boston police tweeted that there is heavy police presence on Franklin Street and asked residents to remain inside.
Dzhokhar, 19, of Russia, is believed to have assault rifles and an assortment of other weapons, including bombs, according to ABC News. Officials are concerned he might try to take hostages.
Dzhokhar has been on the run since about 1 a.m. ET Friday when his older brother, Tamerlan Tsarnaev, was killed in a shootout with police in Watertown after a wild car chase , Boston police said.
During the early-morning shootout, the brothers detonated one pressure-cooker bomb -- like the two explosives used in the deadly Boston Marathon attack -- and also set off several pipe bombs, police said during a Friday afternoon news conference.
Investigators also found several undetonated pipe bombs at the scene.
The younger brother somehow escaped, despite a massive law enforcement door-to-door search of a 20-block area in Watertown. Thousands of police officers, SWAT team members and FBI agents are involved in the search for Dzhokhar.
State police had said that they believe he is on foot, because there's no indication he has a vehicle. It is believed that he may be hurt.
"My message to the suspect is to give himself up," Massachusetts State Police Superintendent Timothy Alben said Friday afternoon.
-- City of Boston at standstill during search --
Police initially warned residents of Watertown, Mass., to stay indoors and not answer the door unless instructed by uniformed police officers. However, that request was extended to the 1 million people in the entire Boston area at 8 a.m. EDT.
Authorities asked residents to stay at home behind locked doors and don't answer the door unless the caller was a law enforcement officer.
But the shelter-in-place order was lifted about 6 p.m. EDT after the fugitive brother appeared to have evaded the Watertown dragnet.
Boston police initially said Dzhokhar may be driving a green 1999 Honda sedan with Massachusetts license plate 116-GC7. However, by 3:45 p.m. ET, Boston police tweeted that they had found the car and were no longer looking for it.
Earlier, Boston police recovered an abandoned gray Honda CRV believed to be the place where the brothers spent the night. It was empty. It is currently being processed for evidence.
For most of the day, Boston streets were empty, with little traffic seen on the roads as area residents were urged to stay indoors. Boston police said AMTRAK service between Boston and New York and all mass transit was suspended. Businesses were asked not to open. People waiting at bus and subway stops were told to go home. The Red Sox and Bruins postponed their Friday games.
Dzhokhar fits the description of Suspect 2, the bombing suspect wearing a white baseball cap in photos released by the FBI Thursday. He has brown, curly hair and was wearing a gray hoodie in a surveillance photograph tweeted by the Boston Police Department.
"We believe this to be a terrorist. We believe this to be a man who's come here to kill people," said Ed Davis, Boston's Police Commissioner.
The brothers' uncle, Ruslan Tsarni, said that the brothers lived together in Cambridge and had been in the United States for about a decade.
Tsarni pleaded with the younger brother to surrender.
"Dzhokar, if you're alive, turn yourself in and ask for forgiveness from victims of the injured."
He called their possible involvement in the bombings an atrocity and said he is shocked that the children of his brother could be involved in the crime wave.
When asked what he thought was the motive for the bombings at the Boston Marathon he said, "Being losers. Hatred for those who were being able to settle themselves ... Anything else to do with religion, with Muslim is a fake."
An aunt said the older brother recently became a devout Muslim, and prayed 5 times a day, and she doesn't believe the brothers could have been involved in Monday's attack.
The brothers are ethnic Chechen who had lived in Dagestan, which neighbors Chechnya in southern Russia.
-- Overnight events --
Authorities suspected the chaotic night of violence began with the robbery of a 7-Eleven in Cambridge.
Then, at about 10:20 p.m. ET, a Massachusetts Institute of Technology campus police officer was repeatedly shot and found in his patrol car. The officer, later identified by the university as Sean Collier, 26, was pronounced dead at a hospital and police said two male suspects were believed to be responsible.
As dozens of local and state police spread across Cambridge searching for the killers, two men reportedly carjacked a black Mercedes SUV.
The carjacked driver was kept inside that SUV for about a half hour before being released at a gas station, the Middlesex District Attorney said.
State Police spokesman Dave Procopio said police realized they were dealing with the bombing suspects based on what the two men told a carjacking victim during their getaway attempt.
Somewhere in the Watertown area, the carjacked SUV was spotted and a police pursuit began.
Gunfire was exchanged and police said explosives were thrown from the SUV during the firefight.
During that shootout, a transit police officer was shot. Richard H. Donohue, Jr., 33, has worked as a officer with the Massachusetts Bay Transportation Authority for three years. He was last listed in critical condition at a Boston area hospital. Collier and Donohue, Jr. are friends, having attended the police academy together in 2010.
The man believed to be Suspect 1, Tamerlan Tsarnaev, was also shot, and later died at Beth Israel Deaconess hospital. Doctors there described him as arriving in a state of "dramatic arrest" and having a combination of blast and gunshot wounds.
Watertown residents reported the sounds of explosions and automatic gunfire early Friday morning. Some tweeted photos of bullet holes in their homes.
The bombings at the Boston Marathon finish line on Monday killed three people and wounded more than 180 others, tearing off limbs in a spray of shrapnel and instantly raising the specter of another terrorist attack on U.S. soil.
Investigators in the Boston case have shed no light on the motive for the bombing and have said it is unclear whether it was the work of domestic or international terrorists or someone else entirely with an unknown agenda.