One of Boston's most notorious mob bosses, James "Whitey" Bulger was found unresponsive in his cell in a federal prison in West Virginia, CNN reports. 

Bulger, 89, was killed on Tuesday morning at the US Penitentiary Hazelton in West Virginia. The Preston County medical examiner pronounced he was dead after they attempted to save his life. He was found unresponsive in his cell around 8:20 a.m. His death is now being investigated by the FBI. The murder of Bulger comes a day after he was transferred to the federal prison in West Virginia from Florida, although 

"Hopefully the seven years he spent in prison, as well as his recent death, brings some closure to the families of his many victims," federal prosecutor Brian Kelly said in a statement. Kelly served as one of the prosecutors in Bugler's trial.

Bulger, who was the former leader of South Boston's Winter Hill Gang, was on the run for 16 years before he was finally captured in California in 2011. He was sentenced to life in prison after he was convicted of numerous crimes, including his involvement in 11 murders, in 2013. His life ultimately went on to inspire several critically acclaimed films such as Black Mass starring Johnny Depp, and The Departed. The latter went on to win the Academy Award for Best Picture in 2006.

While the Department of Corrections hasn't revealed any details pertaining to Whitey's death, three sources told the Boston Globe that an inmate with mob ties is being investigated for the 89-year-old's death.