Infamous Boston gangster James "Whitey" Bulger has been found dead in a US federal prison in West Virginia.
The 89-year-old was discovered unresponsive in his cell at the maximum security facility shortly after being transferred there from a Florida jail.
US media report the former mob boss was killed on Tuesday morning at the penitentiary.
The life of Bulger, who was convicted in 2013 of 11 murders, inspired several films
He was captured in California in 2011 after a 16-year manhunt.
The former leader of South Boston's Winter Hill gang inspired the film Black Mass featuring Johnny Depp, and The Departed, which won the Academy Award for best picture in 2007.
His death comes on the same day that he was transferred to the Hazelton penitentiary in West Virginia, which houses 1,385 inmates, according to reports.
An inmate with mafia ties is now under investigation for Bulger's killing, three sources briefed on the incident told the Boston Globe.
Boston-based WFXT-TV, a Fox affiliate, reports that Bulger was killed hours after being admitted to the general inmate population at the facility.
The Bureau of Prisons declined to comment last week on why Bulger - who was serving a life sentence - was being moved from the Florida penitentiary.
But according to the Globe, Bulger was transferred to Florida in 2014 from another prison in Arizona after his relationship with a female psychologist who was counselling him attracted the attention of prison authorities.
The details of his death have not been announced, but a local union official for correctional workers at the prison told CBS that a "homicide" occurred on Tuesday morning.
"This is the third homicide in seven months at our facility," Richard Heldreth said in a phone interview. "We are very understaffed, we are short about 40 officers."
A Department of Corrections statement on Tuesday confirmed his death in custody, and said the FBI had launched an investigation.
The statement made no mention of the cause of death, but said that "no staff or other inmates were injured, and at no time was the public in danger."
US Attorney for the Massachusetts district Andrew Lelling said that his office had been informed of Bulger's death, adding: "Our thoughts are with his victims and their families."https://www.bbc.co.uk/news/world-us-canada-46036058