Whitey Bulger said to have been killed by inmates 'affiliated with the mob'

James "Whitey" Bulger, the South Boston mobster who was captured after years on the run, was killed in a West Virginia federal prison by at least two inmates, according to two Federal Bureau of Prisons employees who spoke on the condition of anonymity because the information was not yet public.

Bulger, 89, had been transferred to the U.S. Penitentiary, Hazelton in Bruceton Mills, West Virginia, on Monday and was beaten to death shortly after his arrival, according to two of the prison workers. One of the workers said the inmates were thought to be "affiliated with the mob," but did not know the specifics of the association.

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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.

A prison worker said Bulger, who had been serving a life sentence for 11 murders, had been transferred to the Hazelton prison after he had threatened a staff member at the Coleman prison complex in Sumterville, Florida.

The death of Bulger was announced by the Federal Bureau of Prisons on Tuesday, but a cause was not provided. "The Federal Bureau of Investigation was notified and an investigation has been initiated," the news release said. "No staff or other inmates were injured, and at no time was the public in danger."

Bulger had just been moved to the West Virginia penitentiary. It was the latest in a series of prison transfers for him. He had been incarcerated in Arizona, Oklahoma and Florida, prison officials have said, without giving reasons for the moves.