Notorious Boston mobster James “Whitey” Bulger, who led a double life as an FBI informant and once was one of America's most wanted fugitives, was found dead in a West Virginia prison Tuesday, U.S. prison officials said. 

The U.S. Bureau of Prisons said the FBI was investigating the death of Bulger, 89.  

FILE - This June 23, 2011, booking photo provided
FILE - This June 23, 2011, booking photo provided by the U.S. Marshals Service shows James "Whitey" Bulger. The former mobster was found dead in a West Virginia prison Oct. 30, 2018, at age 89.

The Boston Globe, which has long tracked Bulger's life of crime and his 16 years on the run until his 2011 capture, reported another inmate with ties to the Mafia was being investigated in connection with Bulger's slaying. 

Bulger was serving a life sentence, convicted in 2013 of 11 murders and other charges, including racketeering. Authorities said Bulger had gone to great lengths to avoid apprehension, killing potential witnesses and cultivating relationships with corrupt law enforcement officials. 

A tip from a former Icelandic beauty queen led to his arrest in California, where he had been living with his longtime girlfriend, Catherine Greig, now 67. Greig pleaded guilty of harboring Bulger and remains imprisoned in Minnesota. 

Bulger and his Winter Hill gang operated for more than two decades in the Irish-dominated South Boston neighborhood, engaging in loan sharking, gambling, extortion, drug dealing and murder. The gang carried out its operations with the implied consent of an FBI agent who looked the other way at the gang's activities, in exchange for information Bulger supplied about other gangsters. 

Bulger's volatile temper and brutality made him a feared underworld figure. Prosecutors say he used his hands to strangle two women. He tortured a man for hours before shooting him in the head with a machine gun. 

One of his former partners in crime, Kevin Weeks, eventually turned on Bulger and testified against him. 

In his memoir, Brutal, Weeks said, "We took what we wanted. We made millions through extortion and loan sharking and protection. And if someone ratted us out, we killed him. We were not nice guys."