James "Whitey" Bulger, the Boston mob boss who corrupted FBI agents, tortured and murdered his associates and spent 16 years on the run, has been killed in a federal prison while serving a double life sentence. He was 89.
Bulger was killed after arriving on Monday at the US Penitentiary, Hazelton, in Bruceton Mills, West Virginia, after being transferred from a Florida jail.
Stacy Bishop, a spokesperson for US attorney William J Powell, said the death would be investigated but that no other information would be released "at this time".
Anonymous sources, however, told the Boston Globe that a "fellow inmate with Mafia ties" was being investigated in connection with Bulger's death.
Bulger was found unresponsive at 8.20am on Tuesday and pronounced dead by the medical examiner.
"Whitey" Bulger headed a racketeering and drug-dealing operation for 30 years while his younger brother William was president of the Massachusetts Senate. He disappeared in 1995 after learning from a former FBI agent, John J Connolly, that an indictment was pending, triggering a worldwide manhunt.
He was captured on June 22 2011, when a tip-off from a former neighbour led FBI agents to a Santa Monica, California, apartment where Bulger and his girlfriend had been living under false names. Bulger had a stash of 30 guns and $822,000 (R11,700,000) in cash hidden in the walls.
During his two-month trial in 2013, Bulger's former crime partners testified that he took pleasure in killing his victims and sometimes took a nap while his underlings dug graves.
His lawyers attacked the veracity of FBI files allegedly documenting Bulger's years as a criminal informant, giving agents information about Italian organised crime in the US. His defence team claimed he had purchased information from law-enforcement officials, and had never been an informant.
Bulger was convicted of racketeering and the murder of 11 people. Some of his victims, mostly former associates whom he feared were co-operating with police, had been missing for decades until his crime partners led law enforcement to secret graves as part of plea agreements. Bulger was acquitted of seven murders.
"The scope, the callousness, the depravity of your crimes is almost unfathomable," US district court judge Denise Casper told Bulger at his sentencing.
Johnny Depp portrayed Bulger in the 2015 movie Black Mass...