Notorious mobster James "Whitey" Bulger was found unresponsive in his cell at Hazelton Penitentiary

Whitey Bulger Auction - 23 Jun 2016
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James “Whitey” Bulger, the notorious Boston mob boss who spent 15 years on the lam and was the subject of a movie starring Johnny Depp, was found dead Tuesday at a federal prison in West Virginia, PEOPLE confirms.

Bulger, 89, was found “unresponsive” at approximately 8:20 a.m. at Hazelton Penitentiary in Bruceton Mills, the Federal Bureau of Prisons said in a statement obtained by PEOPLE.

“Life-saving measures were initiated immediately by responding staff,” the statement read. “Mr. Bulger was subsequently pronounced dead by the Preston County Medical Examiner.”

The bureau said the FBI is investigating his death. Bulger had been serving two life sentences.

“No staff or other inmates were injured, and at no time was the public in danger,” the statement said.

It is unclear how the mobster died, but three sources told the Boston Globe that a fellow inmate with Mafia ties is being looked at in his death.

The Globe reported Bulger had been at the facility since Monday.

James “Whitey” Bulger
| Credit: REX/Shutterstock

Bulger was convicted in 2013 of 31 federal criminal counts including participating in drug dealing, extortion and murder. He was also convicted of committing or ordering the murders of 11 people during the 1970s and ’80s.

James “Whitey” Bulger
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For nearly three decades, Bulger served as the head of Boston’s Winter Hill Gang. He fled Massachusetts in 1994 after an FBI agent warned him he was about to be indicted. (Bulger had been an FBI informant.)

Bulger spent more than 15 years on the run, but authorities caught up with him in 2011, apprehending him in Santa Monica, California.

Actor Johnny Depp portrayed Bulger in the 2015 film Black Mass.

In 2016, the U.S. Supreme Court rejected his bid to have his convictions overturned.

A statement by U.S. Attorney Andrew Lelling for the District of Massachusetts, which prosecuted Bulger, said, “We received word this morning about the death of James “Whitey” Bulger. Our thoughts are with his victims and their families.”