BOSTON - Hours after the FBI released photos of its two suspects in the Boston Marathon bombings, a massive manhunt began to unfold and several developments happened rapid-fire. Here's a chronological look at the past 24 hours.
Thursday, 5 p.m. -- The FBI releases pictures of two male suspects being sought in connection with the Boston Marathon bombings. Both wore baseball caps, one black, one white, as they walked along a packed sidewalk during the Marathon.
PHOTOS: Photos of the Suspects
PHOTOS: Explosion Aftermath Photos
READ MORE: Expanded Coverage
Late Thursday -- A robbery is reported at a Boston-area convenience store. Police now say that the two suspects were not involved in the robbery, but were present at the time.
Thursday, 11 p.m. -- Police respond to a call on the campus of the Massachusetts Institute of Technology, where university police officer Sean Collier, 26, was shot. He died of his injuries. Police believe the bombing suspects were responsible for the shooting.
Friday, early hours -- Police say the two suspects hijack a car at gunpoint in Cambridge, Massachusetts, taking the driver as a hostage. The hostage is later released unharmed at a gas station.
Friday, 1 a.m. -- Police track the stolen vehicle using its built-in GPS system and pick up the chase in Watertown, Mass. The pursuit winds up in a residential neighborhood, and the suspects hurl explosives and fire shots at officers, officials say.
Friday, 2 a.m.: Transit officer Richard H. Donohue Jr., a 33-year veteran of the force, is shot and wounded in the Watertown exchange. Officers fire back, striking a man. He is later identified as Tamerlan Tsarnaev, and pronounced dead at the hospital. A CNN source briefed on the investigation says Tamerlan Tsarnaev was wearing explosives and an explosive trigger at the time.
Friday, 7 a.m.: At least 12 universities and colleges, along with Boston Public Schools and Cambridge Public Schools, announce that they will be closed for the day due to police activity.
Friday, 8 a.m.: Law enforcement officials identify the dead suspect as Tamerlan Tsarnaev, 26, and the suspect on the run as his brother Dzhokhar Tsarnaev, 19.
Friday, 8 a.m.: Boston-area residents are asked by authorities to stay inside as the hunt continues for Dzhokhar Tsarnaev.
Friday, 9 a.m.: The slain suspect, Tamerlan Tsarnaev, was wearing explosives and an explosive trigger when his body was recovered, a source briefed on the investigation tells CNN.
Friday, 9 p.m.: Dzhokhar Tsarnaev has been found, and is in police custody.