Police secure an area near the Massachusetts Institute of Technology campus in Cambridge, Mass, after a shooting incident involving a campus officer.
BOSTON (USATODAY.com) - The city and its suburbs are in lockdown this morning as a massive manhunt intensifies for the surviving suspect in the Boston Marathon bombing. The search comes just hours after the suspect's older brother was killed in a dramatic firefight with police in nearby Watertown, authorities said.
Authorites are focusing their efforts in Watertown for Dzhokhar Tsarnaev, 19, the brother of the dead suspect, Tamerlan Tsarnaev, 26. The Boston Globeis reporting that police fear Dzhokhar is wearing an explosive vest.
The Tsarnaevs are believed to have moved to the USA from war-torn Chechnya in 2003, along with other family members, a federal law enforcement official said. Tamerlan was studying engineering at Bunker Hill Community College in nearby Charlestown.
Their names were not known to law enforcement officials prior to the bombings, which killed three people and wounded 176. Authorities are reviewing the brothers' possible ties to Chechnya - an area of Russia plagued by Islamic insurgency - a law enforcement official who is not authorized to comment publicly told USA TODAY.
Dzhokhar Tsarnaev is believed to have dropped a backpack laden with explosives at the site of Monday's second explosion. He was pictured wearing a white baseball cap in video images released by the FBI Thursday.
WATCH: Amateur video shows apparent police shootout
A separate law enforcement official said authorities are investigating the brothers' possible link to a third person. The official, who was not authorized to comment publicly, said the identity of person was not immediately clear.
Massachusetts Gov. Deval Patrick ordered the city of Boston and its surrounding suburbs locked down and its residents to remain in their homes. Businesses in Watertown, Newton, Waltham, Belmont, Cambridge and the Alston and Brighton neighborhoods of Boston were requested to remain closed and residents to remain indoors until the suspect is caught. Watertown Police Chief Edward Deveau said his town would be closed to traffic.
Massachusetts shut down all mass transit, including buses and trains, in Boston and surrounding suburbs, Kurt Schwartz, director of Massachusetts Emergency Management Agency said. Schools were closed and classes canceled at most universities.
Massachusetts State Police Superintendent Timothy Alben said Tamerlan Tsarnaev was shot by police in a gunfight following a pursuit that began late Thursday night in Cambridge and ended a short time later in Watertown. He was pronounced dead at a hospital.
LIVE VIDEO: MIT shooting triggers massive police operation in Boston
The manhunt for the marathon bombing suspects turned into hot pursuit at 10:30 p.m., when the two men robbed a 7-Eleven convenience store on the MIT campus in Cambridge, Alben said. Minutes later, an MIT campus police officer was shot multiple times as he was sitting in his car. He was later pronounced dead at Massachusetts General Hospital. He was identified Friday morning as Sean Collier, 26, an MIT police officer since January 2012 and previously a civilian employee at the Somerville Police Department.
SEE ALSO: Images of Marathon bombing suspects released
The suspects carjacked a Mercedes SUV in Cambridge, holding the driver at gunpoint for a half hour before he was released unharmed, according to the Middlesex district attorney's office. Police found the car and the suspects in Watertown, and pursued them into a residential neighborhood where gunfire was exchanged.
A transit police officer, Richard H. Donohue Jr., 33, was reported in critical condition after being shot, police said.
Witnesses report hearing many gunshots.
Alben said the suspects also threw explosives from the car. Residents, witnesses and media in the area heard at least two large booms.
"I heard sirens, then a ton of gunshots,'' said Adam Healy, 31, a behavioral specialist for autism who lives less than a mile from the scene. "And then I heard an explosion amid the gunshots. After the explosion, the sky lit up."
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