BREAKING: One Boston bombing suspect dead, hunt on for second man

Police on Friday killed one suspect in the Boston Marathon bombing during a shootout and mounted a house-to-house search for a second man in the suburb of Watertown after a bloody night of shooting and explosions in the city's streets.

A national security official identified the hunted man as Dzhokar A. Tsarnaev, 19, and said the dead suspect was his brother, Tamerlan Tsarneav, 26. The brothers had been in the United States for several years, the official said.

Authorities locked down much of Watertown and told residents not to leave their homes and not to answer the door as they scoured the area for the missing man, who was described as armed and dangerous. Public transportation throughout the Boston metropolitan area was suspended, and air space was restricted.

During the night a university police officer was killed, a transit police officer was wounded, and the suspects carjacked a vehicle before leading police on a chase that ended with one suspect shot dead