Law Enforcement Officials Say the Two Boston Marathon Bombing Suspects are Brothers

One dead, other still at large. Remaining suspect named as Dzhokhar Tsarnaev by the Associated Press

Authorities shot and killed one suspect in Monday's Boston Marathon bombings and police were searching for a second suspect who was on the loose in Watertown, Mass., early Friday following a chaotic night that left one police officer dead and another critically wounded in the Boston suburbs.

The two men are brothers, ages 20 and 19, law enforcement officials said Friday morning. Their alleged motive in the bombings remains unknown.