Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
WATERTOWN, Mass. - The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area.
The suspects were identified by law enforcement officials and a family member as Dzhokhar and Tamerlan Tsarnaev, brothers from a Russian region near Chechnya, which has been plagued by an Islamic insurgency that has carried out deadly bombings.
Tamerlan Tsarnaev, who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His 19-year-old brother ó dubbed Suspect No. 2 and seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line ó escaped.
The law enforcement officials spoke on condition of anonymity because of the sensitivity of the unfolding case.
Authorities in Boston suspended all mass transit and warned close to 1 million people in the entire city and some of its suburbs to stay indoors as the hunt went on. Businesses were asked not to open. People waiting at bus and subway stops were told to go home.
"We believe this man to be a terrorist," said Boston Police Commissioner Ed Davis. "We believe this to be a man who's come here to kill people."
The bombings 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.
The endgame ó at least for Suspect No. 1 ó came just hours after the FBI released photos and video of the two young men at the finish line and appealed to the public for help in identifying and capturing them. Tips came pouring in to the FBI immediately, but exactly how authorities managed to close in on the two young men was not immediately disclosed.
The men's' uncle, Russian Tsarni of Montgomery Village, Md., told The Associated Press that the men lived together near Boston and had been in the U.S. for about a decade. They traveled here together from the Russian region near Chechnya.
The White House said President Barack Obama was being briefed on developments overnight by Lisa Monaco, his assistant for homeland security and counterterrorism.
The images released by the FBI depict the two young men walking one behind the other near the finish line. Richard DesLauriers, FBI agent in charge in Boston, said Suspect No. 2 in the white hat was seen setting down a bag at the site of the second of two deadly explosions.
Authorities said surveillance tape recorded late Thursday showed Suspect No. 2 during a robbery of a convenience store in Cambridge, near the campus of MIT, where a university police officer was shot to death while responding to a report of a disturbance, said State Police Col Timothy Alben.
From there, authorities said, the two men carjacked a man in a Mercedes-Benz, keeping him with them in the car for half an hour before releasing him at a gas station in Cambridge. The man was not injured.
The search for the vehicle led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer was seriously injured during the chase, authorities said.
In Watertown, witnesses reported hearing multiple gunshots and explosions at about 1 a.m. Friday. Dozens of police officers and FBI agents were in the neighborhood and a helicopter circled overhead.
Watertown resident Christine Yajko said she was awakened at about 1:30 a.m. by a loud noise, began to walk to her kitchen and heard gunfire.
"I heard the explosion, so I stepped back from that area, then I went back out and heard a second one," she said. "It was very loud. It shook the house a little."