Update (4 pm ET): As more details trickle out about the shocking murder of James 'Whitey' Bulger, who was in custody at a maximum security prison in West Virginia and was said to be in ill health at the time of his death, the Boston Globe has reported that a fellow inmate with 'mafia ties' is being investigated for his possible involvement in Bulger's killing.

Bulger earned international notoriety after operating with seeming immunity from federal prosecution thanks to his longstanding cooperation with the FBI. Bulger, a notorious gangster, had been a 'rat' for most of his tenure as a leader of the Winter Hill Gang, the FBI revealed in the early 1990s after it indicted him on multiple accounts of racketeering and other crimes. Bulger, who was tipped off about the pending indictment, fled Boston shortly before he was due to be arrested.

While the details surrounding Bulger's death are still sketchy, he undoubtedly earned many enemies in the Italian mafia thanks to the help he provided the bureau in dismantling the Italian mob in New England.

* * *

Mere hours after he was moved from a federal transfer facility to a prison in West Virginia, notorious Boston crime boss James "Whitey" Bulger, who led the city's Irish mob for more than two decades through a potent mix of cunning and ruthless intimidation, has been killed, according to Fox News.

While the circumstances of his death are unclear, the Associated Press confirmed Tuesday that Bulger had been moved to a prison in West Virginia called USP Hazelton, a high-security prison with near a minimum security satellite camp in Bruceton Mills. The 89-year-old prisoner had recently been moved from a prison in Florida to a transfer facility in Oklahoma City. While the Bureau of Prisons refused to confirm why Bulger had been moved, sources said his health had been deteriorating. The DOJ has launched an investigation into his death. Bulger was found unresponsive in his cell around 8:20 am, the prison said. Staff attempted to resuscitate him, but failed, according to CBS News.

He was serving a life sentence after being convicted in 2013 of a long list of crimes including participating in 11 murders. For 16 years, he topped the FBI's most wanted list after fleeing a pending indictment in 1994 after being tipped off by former FBI agent John Connolly, with whom he grew up in the notorious housing projects of South Boston, and who federal authorities later convicted on accusations that he protected Bulger and essentially operated as a member of his Winter Hill gang. But he was arrested in 2011 in Santa Monica, along with his longtime girlfriend Catherine Grieg, who was sentenced to 21 months in prison back in 2016. She remains behind bars.

Bulger's legend grew after the 2006 film 'The Departed' won Martin Scorsese a 'Best Director' Academy Award. It's chief antagonist, an Irish mob boss played by Jack Nicholson, was said to have been based on Bulger. Like the character in the film, Bulger was exposed for feeding information about underworld rivals to Connolly and the FBI.

As several commenters pointed out on Twitter, the timing of Bulger's death is certainly suspicious, particularly the fact that US media organizations are reporting that he was killed - rather than dying from natural causes - and was found dead at the facility.