Heavily armed police have locked down the entire city of Boston as they search for the surviving suspect in Monday's marathon bombings.
Authorities say one suspect was shot overnight after a gunfight and car chase with police, while the other managed to escape.
The pair is being identified as brothers Dzhokhar Tsarnaev, 19, and Tamerlan Tsarnaev, 26, from the republic of Chechnya in Russia.
Tamerlan was the one killed.
Authorities say the brothers had earlier fatally shot a police officer at MIT.
FBI Photo: surving suspect, 19 Year old Dzhokhar Tsarnaev