NPR's timeline of how events unfolded overnight in the search for the Boston Marathon bombing suspects.
Approximately 5:20 p.m. ET on Thursday: The FBI releases images of two suspects in the Boston Marathon bombings. Suspect No. 1 is wearing a black hat, and suspect No. 2 is wearing a white hat. The FBI urges people to call in with any information.
Approximately 10:20 p.m.: Reports of a robbery at a 7-Eleven store near the Massachusetts Institute of Technology campus in Cambridge.
Approximately 10:30 p.m.: An MIT university police officer is found shot in his vehicle. Sean Collier, 26, is later pronounced dead at Massachusetts General Hospital.
Reports of an armed carjacking in Cambridge. Police say the suspects commandeered a Mercedes SUV, and later released the owner unharmed at a gas station. Police searching for the SUV follow it to Watertown.
Approximately 1 a.m. Friday: Watertown residents report hearing gunfire and the sounds of explosion. Police say the suspects reportedly throw explosives and exchange gunfire with authorities in pursuit. The "black hat" suspect is wounded, and a Massachusetts Bay Transportation Authority officer is shot. The "white hat" suspect flees.
The wounded suspect is taken to Beth Israel Deaconess Medical Center with "multiple traumatic injuries," according to doctors. He is later pronounced dead.
Mass transit is ordered shut down. Several Boston-area neighborhoods are locked down, and police tell residents to stay indoors. Classes at MIT, Harvard and other area schools are canceled for the day.
Approximately 7 a.m.: Law enforcement officials identify the surviving Boston bomb suspect as Dzhokhar A. Tsarnaev, 19, of Cambridge, Mass. They say the suspect who died is his brother.
Reports emerge that a third man, who authorities believe was an accomplice of the bombing suspects, has been arrested.
Approximately 7:55 a.m.: National Security Council officials identify the dead suspect as Tamerlan Tsarnaev, 26.
Approximately 8 a.m.: Officials extend the "shelter in place" advisory to the entire city of Boston. Taxi service in Boston is suspended about 30 minutes later.
Approximately 8:45 a.m.: Law enforcement officials converge on a house in Watertown. Media crews report hearing police on loudspeakers urge someone inside to come out. Police activity there later dissipated.
Approximately 9:45 a.m.: President Obama, Vice President Joe Biden and the national security team hold a White House Situation Room briefing on the investigation and events in Boston and Watertown.
Approximately 10:45 a.m.: Boston police tweet that they have located a 1999 gray Honda CRV that has been linked to the investigation: "Car being processed for evidence by authorities."