UPDATE: 4/19 at 9:37 a.m.
An Associated Press timeline (all times Eastern) 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 of the bombings release photographs and video of two suspects. They ask for the public's help in identifying the men.
- 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 Boston Marathon 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 then released unharmed at a gas station on Memorial Drive 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 transit police officer is seriously injured. One suspect, later identified as Suspect No. 1 in the marathon bombings, is critically injured and later pronounced dead.
- Authorities launch a manhunt for the other suspect.
- Around 1 a.m. Friday, gunshots and explosions are heard in Watertown. Dozens of police officers and FBI agents converge on a Watertown neighborhood. A helicopter circles overhead.
- Around 4:30 a.m., Massachusetts state and Boston police hold a short outdoor news briefing. They tell people living in that section of eastern Watertown to stay in their homes. They identify the carjackers as the same men suspected in the marathon bombings. Overnight, police also release a photograph of a man believed to be Suspect No. 2, apparently taken from store video earlier in the evening at a 7-Eleven convenience store in Cambridge. He is wearing a gray hoodie-style sweatshirt.
- Around 5:50 a.m. authorities urge residents in Watertown, Newton, Waltham, Belmont, Cambridge, Arlington and the Allston-Brighton neighborhoods of Boston to stay indoors. All mass transit is shut down.
- Around 6:35 a.m., The Associated Press reports that the bomb 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 A. Tsarnaev, 19, who has been living in Cambridge.
- Around 8 a.m. Boston's police commissioner says all of Boston must stay in their homes as the search for the surviving suspect in the bombings continues.
- Around 8:40 a.m., a U.S. law enforcement official and the uncle of the suspects confirm that the name of the slain suspect is Tamerlan Tsarnaev, Dzhokhar Tsarnaev's older brother.
UPDATE: 4/19 at 8:01 a.m.
Authorities have identified the transit police officer severely wounded in a shootout with the Boston Marathon bombing suspects.
MBTA Police Chief Paul MacMillan says the wounded officer is 33-year-old Richard Donohue. He is a three-year veteran of the department.
Gov. Deval Patrick says Donohue is in surgery at Mount Auburn Hospital in Cambridge.
The officer was critically injured in an early morning shootout Friday with the two suspects in the marathon bombings. One of the suspects was killed.
Earlier in the night in Cambridge, a Massachusetts Institute of Technology police officer was killed while responding to a report of a disturbance involving the two suspects. The officer died of multiple gunshot wounds.
UPDATE: 4/19 at 7:44 a.m.
A U.S. law enforcement official and the uncle of the suspects in the Boston Marathon bombings are confirming that the name of the second suspect is Tamerlan Tsarnaev, the older brother of Dzhokhar A. Tsarnaev, 19. Tamerlan Tsarnaev was killed in a gun battle with police in Massachusetts overnight.
Three law enforcement officials, speaking on condition of anonymity due to the sensitivity of the ongoing investigation, confirmed the bomb suspects were brothers. One of the officials and the men's uncle confirmed the identity of Tamerlan Tsarnaev.
The uncle, Ruslan Tsarni of Montgomery Village, Md., told The Associated Press that the men lived together near Boston and have been in the United States for about a decade. They traveled here together from the Russian region near Chechnya.
UPDATE: 4/19 at 6:59 a.m.
CBS News reports the two suspects involved in the Boston Marathon bombings have been identified as two brothers from Russia, specifically Chechnya. One suspect has been killed, the surviving suspect has been identified as Dzhokhar A. Tsarnaev, 19, of Cambridge, Mass.
ORIGINAL STORY 4/19 at 2:12 a.m.
CBS News is reporting police have converged on a neighborhood outside Boston where there were reports of explosives being detonated, and police were telling reporters to turn off their cell phones.
Dozens of officers and National Guard members are in Watertown, where media outlets report that gunfire and explosions have been heard. A helicopter is circling overhead.
A police officer told a reporter: "If you want to live, turn off your cell phone."
An employee of CBS Boston station WBZ-TV on the scene says one person has been taken into custody. Another suspect was reported to be at large.
The Associated Press reports police at the Massachusetts Institute of Technology as saying a suspect in the fatal shooting of an officer is no longer on campus.
No arrests have been made in the MIT officer's shooting. The shooter is being sought.
But MIT said Friday on its website it's now "safe to resume normal activities."
Still, it's urging its 11,000 students to "remain vigilant." It had earlier warned them to stay indoors when the shooter was on campus.
The MIT officer was shot Thursday night on the prestigious university's campus just outside Boston. He was pronounced dead later at a hospital.
The shooting comes just days after twin bombings at the Boston Marathon finish line killed three people, wounded more than 180 others and led to an increase in security in the region. Authorities have not yet confirmed a connection.
Information from the Associated Press and CBS News contributed to this report.
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