5 p.m. ET: The FBI releases pictures of two male suspects being sought in connection with the Boston Marathon bombings.
Late Thursday: A robbery is reported at a convenience store. Massachusetts State Police spokesman Col. Timothy Alben initially said the two bombing suspects robbed the store. But he later backtracked, saying the two men didn’t rob a store.
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 from his injuries. Police believe the bombing suspects were responsible for the shooting.
Early hours: Police say the two suspects hijack a car at gunpoint in Cambridge, Massachusetts, taking the driver as a hostage. The suspects tell the driver they are the Boston marathon bombers, a law enforcement source told CNN’s Joe Johns.
Early hours: The hostage is released at a gas station.
Early hours: At one point, the suspects pull over to transfer materials into their new car, two federal officials said.
1 a.m.: Police, who were tracking the vehicle using its built-in GPS system, pick up the chase in Watertown. The pursuit goes into a residential neighborhood, with the suspects throwing explosives and firing shots at officers, police said.
The suspects threw one grenade and five pipe bombs at police chasing them, one FBI and one Department of Homeland Security official told CNN. Three of those explosives detonated, two did not, the officials said.
Officers fire back, with Gov. Deval Patrick later estimating that 200 rounds of gunfire were exchanged in the firefight.
One suspect is hit and run over by the driver of the car he had been in. He is later identified as Tamerlan Tsarnaev, and pronounced dead at the hospital. A source briefed on the investigation says Tamerlan Tsarnaev was wearing explosives and an explosive trigger at the time. After he is shot, his brother runs over him as he drives away, according to the source.
Transit officer Richard H. Donohue Jr., a 33-year veteran of the force, is shot and wounded in the Watertown exchange. Fifteen police officers are treated at St. Elizabeth’s Medical Center in nearby Brighton for injuries suffered in the episode, according to hospital spokeswoman Jennifer Kovalich.
Authorities later announce that they recovered a pressure-cooker bomb after the pursuit into Watertown, a source briefed on the ongoing investigation said. They also recovered a significant amount of homemade explosives in Watertown, Massachusetts State Police spokesman David Procopio said.
2 a.m.: Police begin ordering residents in Watertown to turn off their cell phones.
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 because of police activity.
8 a.m.: Sources identify the dead suspect as Tamerlan Tsarnaev, 26, and the suspect on the run as his brother, Dzhokhar Tsarnaev, 19.
8 a.m.: Boston-area residents are asked by authorities to stay inside as the hunt continues for Dzhokhar Tsarnaev.
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.
All day: Hundreds of law enforcement officers go door-to-door on 20 streets in Watertown, looking for Dzhokhar Tsarnaev. Alben, the state police spokesman, says the suspect fled on foot and that authorities still believe he’s in Massachusetts.
11:30 a.m.: The uncle of the Tsarnaev brothers tells reporters that he is “ashamed” to be related to the suspects, whom he calls “losers.” Speaking outside of his Montgomery County, Maryland, home, Ruslan Tsarni says that his nephew Dzhokhar Tsarnaev “has put a shame on our family, a shame on the entire ethnicity” and should turn himself in.”
12:20 p.m.: The University of Massachusetts-Dartmouth is evacuated, and the school says that Dzhokhar Tsarnaev was an enrolled student. Law enforcement personnel swarm the campus, which is just west of New Bedford and about 60 miles south of Boston.
3:15 p.m.: Numerous activities scheduled for Friday night are canceled around Boston — including Boston Red Sox and Boston Bruins games, as well as a Big Apple Circus show — because of the ongoing manhunt for the marathon bombing suspect.
6 p.m. The lockdown for the Boston area is lifted, meaning people can again leave their homes, even though a suspect remains at large. The area’s public transit system, known as the T, also returns to service after being shut down most of the day, the governor said.
Massachusetts State Police will run additional patrols through Watertown to help police in that city, for at least the next few days or until Dzhokhar Tsarnaev is caught or killed, said Alben.
6:30 p.m.: Interpol issues an “international security alert” related to the marathon bombings, asking its 190 member countries to look for information tied to the case and, specifically, information about bombs similar to those used in the attack. The international law enforcement agency’s Orange Notice includes photographs of the bombs used on Monday and fingerprints of the two suspects.
7:30 p.m.: A senior federal law enforcement official says authorities in Watertown, Massachusetts, have engaged the possible remaining suspect in the marathon bombings.
7:45 p.m.: As many as a dozen people were moved away from the scene of intense police activity in Watertown, Massachusetts, including a young girl being carried in a police officer’s arms. There was a large police presence and a helicopter flying overhead. Witnesses said they’d heard about 20 gunshots fired.
8:00 p.m.: There are multiple explosions near where authorities have engaged the possible suspects.
8:15 p.m.: A person believed to be Dzhokar Tsarnaev is cornered on a boat in a yard in Watertown, Massachusetts, law enforcement officials say.
8:30 p.m.: Law enforcement officials make a number of appeals to the person apparently inside the boat: “Come out on your own terms”; “We know you’re in there” and “Come out with your hands up.”
8:35 p.m.: While executing a search warrant in New Bedford, Massachusetts, at a residence believed to have been affiliated with Dzhokhar Tsarnaev, the FBI takes three people — two males and a female — into custody for questioning Friday evening, according to New Bedford Police Lt. Robert Richard. The residence searched by the FBI is private off-campus housing for UMass Dartmouth students, Richard said.
8:43 p.m.: Police in Watertown, Massachusetts, break out in cheers, shouting “Yay!” A crowd of neighbors also cheer.
8:46 p.m.: The Boston Police Department tweets: “Suspect in custody. Officers sweeping the area. Stand by for further info.”
Suspect in custody. Officers sweeping the area. Stand by for further info.—
Boston Police Dept. (@Boston_Police) April 20, 2013
CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody.—
Boston Police Dept. (@Boston_Police) April 20, 2013
CNN’s Brian Todd, Jason Carroll, Adam Levine, Jason Kessler and Wayne Drash contributed to this report