WATERTOWN, Mass. (AP) -

Two suspects in the Boston Marathon bombing -- identified to The Associated Press as coming from the Russian region near Chechnya -- killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said.

A law enforcement intelligence bulletin obtained by the AP identified the surviving bomb suspect as Dzhokhar A. Tsarnaev, 19, of Cambridge, Mass.

Two law enforcement officials told AP that Tsarnaev and the other suspect who was not immediately identified have been living legally in the U.S. for at least one year.

Russia's North Caucasus region has been plagued by an Islamic insurgency stemming from separatist wars in Chechnya.

PREVIOUS STORY

Authorities say one of two suspects in the Boston Marathon bombing is dead and a massive manhunt is underway for another.

Residents of the Boston suburb of Watertown have been advised to keep their doors locked and not let anyone in.

The Middlesex district attorney says the two men are suspected of killing an MIT police officer at the college late Thursday, then stealing a car at gunpoint and later releasing its driver unharmed. Hours earlier, police had released photos of the bombing suspects and asked for the public's help finding them.
Authorities say the suspects threw explosives from the car as police followed it into

Watertown. The suspects and police exchanged gunfire and one of the suspects was critically injured and later died.

Police say the suspect on loose is a "terrorist" who "came here to kill people."