The former head of the feared Winter Hill gang James Bulger, known by his alias "Whitey," was found dead Tuesday morning in a West Virginia prison.

According to NBC, Bulger, 89, who was serving a life sentence, was relocated from a Florida prison to an Oklahoma facility on Oct. 25, though it remained unclear why he was being transferred. From there, he was sent to USP Hazelton, a high-security penitentiary in Bruston Mills, WV.

Bulger's crime syndicate became a large part of Boston's underground, as his tenure was comprised of his involvement in murders, as well as a number of other crimes which included money laundering and extortion. His life events inspired a list of movies, including the 2006 film The Departed.

In 2013, the mob boss was convicted of a string of murders (11 total) that occurred in the 1970s and 1980s. He was subsequently sentenced to life in prison. In Oct. 2013, he attempted to appeal the racketeering conviction and life sentence, but was ultimately denied.

In response to the death of Bulger, as spokeswoman for the West Virginia District Attorney's office stated "the FBI will be conducting an investigation into the death of James Bulger. No other information will be released at this time."

Prison officials found Bulger deceased just hours after he arrived at USP Hazelton. According to the Boston Globe, individuals who were briefed of the murder say that a fellow inmate with Mafia connections is currently being investigated.