BOSTON -- Key moments related to the search for the Boston Marathon bombing suspects, based on reports from the Middlesex County district attorney, Massachusetts State Police and Boston police.
At 5:10 p.m. Thursday, investigators release photographs and video of two suspects and ask for the public's help in identifying them.
Around 10:20 p.m., shots are fired on the campus of the Massachusetts Institute of Technology in Cambridge, just outside Boston.
At 10:30 p.m., an MIT campus police officer who was responding to a disturbance is found shot multiple times in his vehicle, apparently in a confrontation with the bombing suspects. He is later pronounced dead.
Shortly afterward, two armed men reportedly carjack a Mercedes SUV in Cambridge. A man who was in the vehicle is held for about a half hour and released unharmed at a gas station in Cambridge.
Police soon pursue the carjacked vehicle in Watertown, just west of Cambridge.
Some kind of explosive devices are thrown from the vehicle in an apparent attempt to stop police. The carjackers and police exchange gunfire. A police officer is seriously injured. One suspect is critically injured and later pronounced dead.
Authorities launch a manhunt for the escaped suspect.
Around 1 a.m. Friday, gunshots and explosions are heard in Watertown. Dozens of police officers and FBI agents converge on a Watertown neighbourhood.
Around 4:30 a.m., Massachusetts state and Boston police tell people living in that neighbourhood to stay indoors. They identify the carjackers as the same men suspected in the bombings. Overnight, police release a photograph of one of the suspects. The image apparently was taken from surveillance video at a gas station in Cambridge.
Around 5:50 a.m. authorities urge residents in Watertown, Newton, Waltham, Belmont, Cambridge, Arlington and the Allston-Brighton neighbourhoods of Boston to stay indoors. All mass transit is shut down.
Around 6:35 a.m., The Associated Press reports the suspects are from a Russian region near Chechnya and lived in the United States for at least a year.
Around 6:45 a.m., The Associated Press identifies the surviving Boston bomb suspect as Dzhokhar Tsarnaev, 19, who has been living in Cambridge.
Around 8:40 a.m., a U.S. law enforcement official and the uncle of the suspects confirm the name of the slain suspect is Tamerlan Tsarnaev, Dzhokhar's older brother.
Around 10:20 a.m., Connecticut State Police say a grey Honda Civic believed to be linked to Dzhokhar has been recovered in Boston.
Around 10:35 a.m., the University of Massachusetts Dartmouth says it closed its campus and ordered an evacuation after confirming Dzhokhar is registered there.
Around 12:35 p.m., state police in Watertown say officers are searching door-to-door but still have not found the bombing suspect.
Around 6:30 p.m., Massachusetts Gov. Patrick Deval announces mass transit is resuming and the "stay indoors" order is being lifted, even though Dzhokhar remains on the lam. State police say he fled on foot and there are no indications he has a vehicle. They believe he is still in the state because of his ties to the area.
Around the time the order is lifted, a flurry of gunfire breaks out in the community that was being searched. Law enforcement officials locate Dzhokhar Tsarnaev in a boat parked behind a home.
At approximately 8:45 p.m., Dzhokhar Tsarnaev is taken into custody by police.
-- The Associated Press