3 men charged in connection with death of gangster James 'Whitey' Bulger

Three men were charged Thursday in connection with the 2018 death of notorious mobster James "Whitey" Bulger, federal prosecutors announced.

Bulger was allegedly bludgeoned to death in federal prison, according to prosecutors, by Fotios Geas, 55, also known as "Freddy," and Paul J. DeCologero, 48, known as "Pauly." Both are charged with conspiracy to commit first-degree murder. A third man, Sean McKinnon, 36, is charged with making false statements to a federal agent and conspiracy to commit first-degree murder.

Bulger was transferred to United States Penitentiary Hazleton in Bruceton Mills, West Virginia, and shortly thereafter was murdered at the federal prison on Oct. 30, 2018.

Bulger, the leader of Boston's Winter Hill gang, was on the run for 16 years before being caught by federal authorities, and later tried and convicted. Before being moved to a West Virginia lockup, the 89-year-old was housed in federal prison in Florida.

Geas is still incarcerated at USP Hazelton, according to prison records, and is serving a life sentence for a separate crime. DeCologero is no longer being held at USP Hazelton but remains housed in the federal prison system, and McKinnon was on federal supervised release at the time of the indictment and was arrested Thursday in Florida.

Bulger, who was serving a life sentence, was moved to West Virginia for no real reason, according to a lawsuit filed by his family.

He had suffered multiple heart attacks and was confined to a wheelchair, a source familiar with his condition told ABC News, leaving his attorneys puzzled over how Bulger's medical condition suddenly improved so much that he was able to move prisons.

"Mr. Bulger's physical/medical condition was fraudulently upgraded to effectuate a transfer and place to Hazelton on or about Oct. 29 or Oct. 30, 2018," attorneys Hank Brennan and David Schoen wrote in an administrative claim against the Department of Justice, a copy of which was obtained by ABC News and was filed in 2019.

"To be clear, we do not believe that the transfer to Hazelton and placement in general population was simply dangerous, negligent, reckless and irresponsible; we believe it was also intentional and part of conspiracy among BOP, DOJ employees and others to intentionally cause Mr. Bulger's serious injuries and death," the complaint said.

Bulger's death inside the federal prison is just one high-profile death that has not seen resolution, another other being the suicide of Jeffery Epstein in a Manhattan lockup.

The Bureau of Prisons has not responded to ABC News' request for comment.