An ex-Mafia hitman who’s being eyed as the prime suspect in the fatal beatdown of James “Whitey” Bulger can guarantee his status as a boss behind bars — if he really was behind the infamous Boston gangster’s death.

Fotios “Freddy” Geas is suspected of rubbing out Bulger, 89, on Tuesday morning — hours after the aging mobster was transferred to Hazelton federal penitentiary in West Virginia.

“He’s a rich man now. He’ll run any prison he’s in,” a law enforcement source told MassLive.com.

Geas, 51, is serving a life sentence at Hazelton for the 2003 murders of one-time mob boss Adolfo “Big Al” Bruno and associate Gary Westerman.

The former West Springfield, Massachusetts, resident has not disputed his role in the death of Bulger, according to the Boston Globe.

A law enforcement source said the wheelchair-bound Bulger was “badly beaten” by a group of inmates, including one who used a padlock wrapped in a sock. He was found unresponsive in his cell just after 8 a.m.

As the boss of the lucrative and violent Winter Hill Gang, Bulger cemented his crew’s position as the most powerful in Boston by secretly serving as an informant for the FBI from the mid-1970s through the ‘90s. The deal protected him from prosecution while he gleaned key information about sting operations and rival gangsters.

Geas has an open hatred for “rats” — making Bulger a prime target.

“He has great disdain for informants,” Daniel D. Kelly, a lawyer who represented both Geas and his younger brother Ty Geas in several criminal cases, told MassLive.com. “I’m not saying Freddy did this just because the media says so, I’m just telling you what I know about him.”

“Freddy is a dying breed,” added Kelly, who’s pals with Geas and frequently exchanges emails with him.

Geas has led a life of crime, with a rap sheet dating back to his teens. He and his brother Ty were convicted of killing Bruno, a Genovese capo, “cowboy style” in 2003.

Geas hired the hitman in Bruno’s murder — but shot Westerman twice in the head himself after luring him to a home in Agawam for a purported home invasion.

The Geas brothers served as hitmen for Anthony Arillotta, who became a made man in the Mafia in 2003 but then flipped by becoming an FBI informant after he and the two men were charged in Bruno’s murder.

Arillotta wound up serving 99 months in exchange for his testimony against the brothers and others and has since entered witness protection.

Geas wasn’t swayed one bit by Arillotta’s cooperation, despite knowing he was facing a life sentence, according to Kelly.

“Freddy is a man’s man,” the attorney said. “After Anthony Arillotta flipped, there was a back channel for Freddy to try to persuade him to cooperate too. He didn’t even blink an eye. He didn’t flinch. He just said no.”

The lawyer said he chatted with Geas just a few days before Bulger’s death — but only discussed typical Boston topics.

“The Patriots,” said Kelly. “We talk about sports and weather, like everyone else.”