WATERTOWN, Mass. (AP) – 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 run, authorities said Friday as thousands of officers swarmed the streets in a manhunt that paralyzed the Boston area.

The suspects were identified by law enforcement officials and family members as Dzhokhar and Tamerlan Tsarnaev, ethnic Chechen brothers from Dagestan, which neighbors Chechnya in southern Russia. They lived near Boston and had been in the U.S. for about a decade, an uncle said.