A scene of chaos descended on Cambridge and Watertown late Thursday night and early Friday morning, as police confirmed that a Massachusetts Institute of Technology police officer was shot and killed, and an apparent carjacking led police on a wild chase into Watertown in pursuit of the Boston Marathon bombing suspects.

A law enforcement official told The Boston Globe that the suspect at large after a firefight in Watertown is Dzhokhar A. Tsarnaev, 19. The deceased suspect is Tsarnaev’s brother, an official said. The Associated Press reports that the men are from an area in Russia near Chechnya and lived in the United States for at least one year.

This surveillance photo taken from a convenience store and released via Twitter by the Boston Police Department on Friday shows a suspect that police are searching for in Watertown.

The FBI also released this image of Dzhokhar Tsarnaev on Friday.

Helicopters hovered over mobile television dishes while engaged in the search for bombing suspect Dzhokhar A. Tsarnaev.

SWAT team members conducted a door-to-door search over a large swath of Watertown for the bombing suspect.

Law enforcement officers wearing tactical gear left the search area earlier today.

UMass Dartmouth, where Dzhokhar A. Tsarnaev was a student, was evacuated Friday. Above, one of two military-style helicopter landed on the campus.

State, local, and federal agents gathered at a rear parking area in apparent preparation to probe Dzhokhar A. Tsarnaev’s dorm room.

A truck was removed from the crime scene on Nichols Avenue in Watertown.

Black Hawk helicopters hovered above the Watertown crime scene.

Boston police walked down Mt. Auburn Street while searching for the suspect.

Police questioned residents of the building on Norfolk Street in Cambridge where at least one of the bombing suspects lived.

A man holding a child looked down as police questioned residents of the Norfolk Street building.

FBI agents walked past a Cambridge police bomb squad van on Norfok Street in Cambridge, where at least one of the bombing suspects lived.

Police navigated a bomb disposal robot near the Cambridge police bomb squad van.

Heavily armed FBI agents gathered next door to the Norfolk Street home.

Among those who spoke Friday afternoon in a news conference at the Watertown Mall were Boston Mayor Thomas M. Menino (seated) and Governor Deval Patrick.

Police in West New York, N.J., collected evidence from the apartment of Alina Tsarnaeva, sister of the Boston Marathon bombing suspects, on Friday.

Maret Tsarnaeva, an aunt of the suspects in the Boston Marathon bombing, held a reporter's smart phone displaying a scene from the bomb site as she spoke to journalists in the lobby of her apartment building in Toronto.

The father of the Boston bomb suspects, Anzor Tsarnaev, spoke to the media Friday. “My son is a true angel,” his father told the Associated Press. Anzor Tsarnaev also said his sons were set up, and said “all hell will break loose” if his other son is killed.

Ruslan Tsarni, the uncle of Tsarnaev, urged his nephew to surrender while speaking with the media outside his home in Montgomery Village in Maryland.

A sign calling for citizens of Boston to "Shelter in Place" is shown on Interstate 93 in Boston.

Police ran down the street in Watertown.

Police aimed their weapons in a Watertown neighborhood that was locked down.

Residents are led out of their homes in Watertown.

Katia Costa looked out her apartment window with a cup of coffee at the police activity below on her street in Watertown.

People waited to cross the street at the University of Massachusetts-Dartmouth after the campus closed when school officials learned that one of bombing suspects is a student at the school.

A dorm at the Southeastern Massachusetts school was also evacuated earlier on Friday.

A Boston police officer in protective gear took aim at a building in Watertown.

Members of a SWAT team walked down a street in Watertown.

Police vehicles clogged a Watertown neighborhood.

Residents watched police activity in Watertown.

A law enforcement official stood with a police dog in Watertown.

President Obama met with members of his national security team earlier Friday to discuss developments in the Boston bombings investigation. From left: FBI Director Robert Mueller, Assistant to the President for Homeland Security and Counterterrorism Lisa Monaco, Attorney General Eric Holder, Deputy National Security Adviser Tony Blinken, and Vice President Joe Biden.

Tsarnaev is pictured in a yearbook photo.

Tamerlan Tsarnaev (left) is shown in this February 2010 photo accepting the trophy for winning the New England Golden Gloves championship.

Tamerlan Tsarnaev, with Somerville boxing club trainers, had his hands laced during a May 2006 bout at the Golden Gloves boxing tournament in Lowell.

FBI agents searched homes in Watertown for Dzhokhar Tsarnaev.

A police officer evacuated a shoeless man holding a child during a search in Watertown.

Police searched for Tsarnaev at an apartment building where a resident reported finding drops of blood in Watertown.

A law enforcement bomb technician walked away after preparing a controlled detonation of a suspicious object during a search for Tsarnaev.

Police hunted for Tsarnaev in Watertown.

SWAT teams moved into position in Watertown.

Governor Deval Patrick arrived to speak to the media at the Watertown Mall in Watertown.

State troopers lined up Arsenal Street in front of the Arsenal Mall in preparation for Governor Patrick to address members of the media in Watertown.

A member of the SWAT team trained a gun on an apartment building during a search for Tsarnaev in Watertown.

A SWAT team arrived in Watertown.

A SWAT team drove down a street in Watertown.

Residents watched police activity from their windows in Watertown.

Officials are gathered outside a building in Watertown.

An armed official stood outside a building in Watertown.

An armed officer checked a personal device on a street in Watertown, where a firefight erupted after the death of a MIT police officer.

Officials cordoned off a street in Watertown.

An armed official headed inside a cordoned off area in Watertown.

A neighbor watched police activity from her car in Watertown.

Governor Deval Patrick shut down MBTA service on Friday. Staff stood near a Green Line trolley car in Cleveland Circle.

A bomb disposal robot checked out a car in Watertown during a manhunt for the Boston Marathon suspects.

Two men carjacked a Mercedes SUV at gunpoint, and the owner of that car was able to flee at a gas station, pictured, on Memorial Drive in Cambridge.

Col. Timothy P. Alben, superintendent of the Massachusetts State Police, spoke to reporters about the status of the search.

A law enforcement official stood with his rifle during a search in Watertown. Police warned Watertown residents not to open their doors and said they would conduct a door-to-door, street-by-street search due to what it called a fluid situation.

Police officers aimed their weapons in Watertown.

Law enforcement officials staged in a parking lot during a search.

Police officers (not pictured) kept a man on the ground in Watertown after the fatal shooting of a police officer at the Massachusetts Institute of Technology.

A police officer told a driver to turn around on a street in Watertown.

Boston Police gathered in the parking lot in front of a Best Buy store near the Watertown Mall in Watertown.

Police officers aimed their weapons in Watertown.

The scene in Watertown was tense.

A police official looked over an object that was picked up by a remote control device in Watertown.

Police searched neighborhoods yard by yard after a police chase and shootout with two heavily armed men in the wake of the shooting of an MIT police officer.

Police from several different agencies searched the scene of a shootout that followed a carjacking in Watertown.

A police officer with a gun drawn searched for a suspect in Watertown.

Police from several different agencies searched the scene of a shootout that followed a carjacking in Watertown.

Police with guns drawn positioned themselves behind police cruisers.

A member of the media filmed the scene in Watertown.

A vehicle carrying officers in tactical gear arrived at a Watertown neighborhood.

Police vehicles searched neighborhoods yard by yard.

Law enforcement swarmed a Watertown neighborhood.

A Boston police boat patrolled the Charles River near MIT.

Boston police Superintendent in Chief Daniel Linskey and Superintendent William Evans, right, were in Cambridge after a reported shootout on Mt. Auburn Street .

A street was cordoned off by police.

MIT and Cambridge police responded to a report of shots fired about 10:30 p.m. near Main and Vassar streets, said State Police spokesman Dave Procopio.

According to a tweet from the Massachusetts Institute of Technology, “there is a report of an active shooter in the vicinity” of Building 32, the renowned Stata Center, pictured on the left.

Massachusetts State Police, Cambridge Police, and MIT police searched the scene of the reported shooting on April 18.

Police officers and canine units swarmed the campus, and a big swath of Vassar Street was blocked.

Officers walked in a group with flashlights scanning bushes and the sidewalk by Vassar Street.

MIT Police Chief John DiFava is pictured at left in Cambridge.

Police remained on the scene as Thursday night turned to Friday morning.

Police extended yellow tape farther down Vassar Street in Cambridge just before midnight.

ATF officers searched behind the Stata Center.

Police searched neighborhoods door to door.

Police worked a crime scene in Watertown.

On scchool vacation week, 12-year-old Paulo Costa watched on TV what was across the street from his apartment window: the search for the Boston Marathon bombing suspects.