Geriatric mobster James “Whitey” Bulger was wrapped in a blanket to appear like he was asleep in his bed — with his head resting on the pillow — after being bludgeoned to death in prison, according to a report.

Law enforcement sources told NBC News that Bulger’s killers took the concealment measures after pummeling the 89-year-old Boston crime boss with a padlock stuffed in a sock.

Authorities believe that former Mafia hitman Fotios “Freddy” Geas and Paul DeCologero of the North Shore organized crime group attacked Bulger after he arrived at the Hazelton federal lockup in West Virginia, according to the Boston Globe.

He was found unresponsive about 8:20 p.m. Tuesday.

The officials told NBC that the federal investigation also is reviewing the circumstances surrounding Bulger’s transfer from a Florida prison to the violence-plagued West Virginia one.

The prison has been suffering from a staffing shortage resulting from the Trump administration’s order of a federal hiring freeze last year, officials said. In the last six months, two other inmates were killed at Hazelton.

Bulger, an FBI rat who ran Beantown’s Irish mob, was transferred from the Coleman penitentiary in Florida because of multiple infractions, according to NBC News.

In 2015, he was cited for masturbating in front of a male staffer, according to prison records cited by the news outlet. In February, he threatened a nursing supervisor.

“Your day of reckoning is coming,” Bulger told the worker, a law enforcement source told NBC.

He was placed in solitary until Oct. 23, when he was sent to a transfer facility in Oklahoma before being shipped to West Virginia.

Bulger arrived at Hazelton at 6:45 p.m. Monday and was placed in a cell at 9:53 p.m., when the housing unit was already on lockdown, prison sources told NBC News.

But when a new inmate arrives, other prisoners usually take notice, a staffer said. “It’s almost like you see in the movies,” the worker told the outlet.

Bulger agreed to be placed with the general population, law enforcement sources said.

Documents obtained by the network show Bulger, who had been suffering from heart trouble, was classified as a level two, a lower classification than when he was in other prison medical facilities.

But some prison worker and union officials said they were surprised that he wasn’t placed in an area where high-profile inmates are separated from the general population.

“I thought it was unusual that this specific inmate was placed in general population in our facility given the level of violence and the type of inmates housed there,” prison union head Rick Heldreth told NBC News.

“That decision would have been far above us,” Heldreth said, adding that his reputation as a snitch would have made him a target.

“In general population, you’re in a housing unit with 120 inmates and they have full access to you,” he said. “I know how he’s been labeled in the court system and that’s not something that goes over well with our inmate population.”