The search for the Mercedes 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, 33-year-old Richard Donohue, was shot and critically wounded, authorities said.
Dzhokhar Tsarnaev somehow slipped away; his brother died at a Boston hospital after suffering what doctors said were multiple gunshot wounds and a possible blast injury.
The brothers had built an arsenal of pipe bombs, grenades and improvised explosive devices and used some of the weapons as they drove off in the stolen car, said Rep. Dutch Ruppersberger, D-Md., a member of the House Intelligence Committee.
Watertown resident Kayla Dipaolo said she was woken up overnight by gunfire and a large explosion that sounded "like it was right next to my head ... and shook the whole house." She said she was looking at the front door when a bullet came through the side paneling. SWAT team officers were running all over her yard, she said.
"It was very scary," she said. "There are two bullet holes in the side of my house, and by the front door there is another."
Christine Yajko said she heard two loud explosions and gunfire. She said a police officer later knocked on her door and told her there was an undetonated improvised explosive device in the street and warned her to stay away from the windows.
"It was on the street, right near our kitchen window," she said.
Tsarni, the men's uncle, told The Associated Press that the brothers traveled here together from Russia. He called his nephews "losers" and said they had struggled to settle in the U.S. and ended up "thereby just hating everyone."