AP sources identify the man as 19-year-old Dzhokhar Tsarnaev (JOH'-kahr tsar-NY'-ehv), of Cambridge, Mass. He is the bombing suspect who is still alive. The other bombing suspect was killed overnight in an exchange of gunfire with police.
The sources also say both men are from a region of Russia near Chechnya, and have lived in the U.S. for at least a year.
Police are locking down some neighborhoods in Boston and its western suburbs as they search for the remaining suspect in the marathon bombings.
Authorities urged residents in Watertown, Newton, Waltham, Belmont, Cambridge and the Allston-Brighton neighborhoods of Boston to stay indoors. All mass transit was shut down.
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."
Police say one of two suspects in the shooting of an MIT police officer is dead and a massive manhunt is underway for another, who is tied to the Boston Marathon bombing.
Shortly after the MIT officer was shot Thursday night, police got a report of a carjacking in Cambridge, just outside Boston.
Police say of the at-large suspect, "We believe this to be a terrorist."
The FBI is investigating whether the shooting of a campus police officer at the Massachusetts Institute of Technology and gunfire and explosions in a nearby town are related to the Boston Marathon bombings.
A Massachusetts State Police spokesman says one person suspected in the gunfire and explosions has been accounted for and one is at large.
The FBI says it is working with local authorities to determine what happened.
The MIT shooting on the Cambridge campus Thursday night was followed by reports of violence in nearby Watertown, about 10 miles west of Boston.
A state police spokesman said early Friday there is a "strong possibility" the incidents are related.
Cab driver Imran Sais says he heard "a loud boom" while standing on a street corner at a police barricade across from a diner.