A senior law enforcement official who oversees organized crime cases but was not involved in the investigation into Bulger's death, said he was told by a federal law enforcement official that an organized crime figure was believed to be responsible for the killing.
Bulger had just been moved to the Hazleton facility where he was found.
Bulger, 89, had recently arrived at the high-security penitentiary USP Hazelton in West Virginia, according to the Boston Herald.
Bureau of Prisons officials and his attorney did not say why he was being moved, but he was known to have medical ailments.
Bulger was 89 years old.
In addition to his role in murders, Bulger was also convicted for racketeering. He was sentenced to serve two consecutive life sentences plus five years.
The tale became the basis for the 2006 Oscar-winning film "The Departed", which starred Jack Nicholson as a character modeled on Bulger.
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In February 2015, Bulger made headline news after he penned a letter to three teenagers who reached out to him for a school project.
A man who lived by violence, vengeance and intimidation, Bulger would not make eye contact at his sentencing with the relatives of the people he'd killed, nor those who were slain by his accomplices in the treacherous Winter Hill Gang.
Bulger would pen notes on his lawyer's legal pad at his cell in MA back in 2014 and have them delivered via his lawyer to Greig who was detained at a Rhode Island Jail at the time. But in his case, it was never clear who was informing to who.
"You could go back in the annals of criminal history and you'd be hard-pressed to find anyone as diabolical as Bulger", said Duffy.
"I thought they had him under a lot of security", she said.
The FBI had been searching for Bulger for 16 years before his arrest.
She may not even know that her beau, the notoriously murderous "Whitey", is dead as she's now detained in Waseca, Minnesota serving out her eight-year jail sentence.