One police officer also killed, second suspect said armed and dangerous.
Two men terrorized Bostonians with violence overnight, and police believe they could be the same men who planted bombs that killed three in the Boston Marathon Monday.
One of the suspects is dead after a shootout with police, said spokesman Captain Paul MacMillan.
The other man is still at large, he warned, and believed to be armed and dangerous. Officers from various police departments and the FBI are searching house to house in the neighborhood of Watertown, Massachusetts, to try to track him down.
One of the Boston bombing suspects reportedly died on Friday after a shootout with police, as explosions rang out near the tense US city and officers stayed on the hunt for a second suspect.
The manhunt began after a campus police officer was killed at the elite Massachusetts Institute of Technology, the Boston Globe reported, days after the city's historic marathon came under attack.
Police in Watertown, Massachusetts, are looking for a suspect in the Boston Marathon bombing, officials said early on Friday.
'We believe this to be a terrorist. We believe this to be a man who has come here to kill people. We need to get him in custody', said Boston Police Commissioner Edward Davis.
The suspect police are looking for in Watertown is the one seen in images released by the FBI of a man wearing a white cap, Davis said.
The other suspect in those images was killed during a pursuit by officers, police said.
Police said the two men are suspected of killing a police officer on campus at the Massachusetts Institute of Technology (MIT) late on Thursday.
They then stole a car at gunpoint and drove away with the car's owner still on board.
They later released the driver unharmed.
The men threw bombs and traded gunfire with police before being stopped at Watertown.
One suspect was hit by bullets during the chase and later died, police said.
image: © Bengt Nyman