Jimmy Hoffa was killed on July 30, 1975, in a plot involving two Detroit Mafia brothers and Frank Fitzsimmons, who was the president of the Teamsters Union at the time, according to Hoffa’s son, James P. Hoffa.

“They had it set up to murder him, and they did,” Hoffa said..

“They decided to murder him because there was no other way to stop him. He was a powerful and unstoppable figure,” said Hoffa about his famous father, who was gearing up to challenge Frank Fitzsimmons for the International Brotherhood of Teamsters presidency in 1976.

“Fitzsimmons feared Hoffa’s return, wanting to retain his position. The Mafia didn’t want him back, so I believe they collaborated. They discussed, ‘How can we ensure he won’t come back?’ They were frightened because they knew if Hoffa came back, he would win the election and take control of the union. The only sure way to prevent that was to eliminate him.”

The stunning revelations from the younger Hoffa, a former Teamsters president himself, are aired in an exclusive Fox Nation interview. Hoffa opened up about his father’s disappearance for the last two episodes of the streaming series “Riddle, The Search for James R. Hoffa.”

“It was just devastating to my family, to my sister,” Hoffa said. “My father was everything, and my mother died five years later of a broken heart. She never got over it.”

“We don’t have closure because we don’t have a grave. And it’s amazing what that means to people,” he continued. “We are left with the love of him, but what else do you have? We have a hole in our heart.”

“My father is gone, and he was a great man, and that’s the great loss to my family and to the union.”

Hoffa told Fox Nation that Fitzsimmons, who died of lung cancer in 1981 at the age of 73, was a member of the conspiracy that was hatched by the Detroit mob crime family to get rid of his father. He said the assassination plan was carried out by Mafia capos Anthony Giacalone, known as “Tony Jack,” and his capo brother Vito Giacalone, known as “Billy Jack.”

“He was pushing very hard against powerful people in the union and obviously in the mob,” he said. “They realized the only way to stop him was to kill him.”

Fox Nation has also learned about a new claim from a Detroit mobster who told the FBI he witnessed Hoffa’s murder and named Vito “Billy Jack” Giacalone as the killer. The informant said he would refuse to testify and would deny he admitted it if ever confronted, according to the claim.

Another new accusation comes from former Detroit mobster Nove Tocco, who said that “Tony Jack” Giacalone told him that Hoffa was killed by another mobster, Anthony Palazzolo, known as “Tony Pal,” according to Detroit mob reporter Scott Burnstein, who runs the website “Gangster Report.”

The FBI would not confirm the claims. Palazzolo’s family refused to comment to Fox Nation and Vito “Billy Jack” Giaclone’s son, 74- year old Jackie Giacalone, who has been publicly listed as the reputed current head of the Detroit mob, previously told Fox Nation that he has no idea what happened to Hoffa.

“I believe Jimmy Hoffa was part of the ozone layer within 90 minutes of disappearing,” said Vince Wade, a veteran Detroit television reporter who broke the story of Hoffa’s disappearance in 1975. “I believe the body was totally destroyed.”

The preponderance of the evidence points to the waste facility, Central Sanitation Services in Hamtramck, Mich., a short drive over the Detroit city line, as the place where Hoffa’s body was taken.

“It was run by the Mob, so they could control who was around and who wasn’t around. If you don’t have a body, you don’t have evidence. And if you don’t have evidence, you don’t have a case,” said Wade.

“It had those huge compactors which would crush tons of cardboard into miniscule pieces of cardboard, said Keith Corbett, the former head of the Justice Department Organized Crime Strike Force in Detroit. “That would have been the perfect place.”

David Tubman, who has researched the case extensively and written the book “Jimmy Hoffa Is Missing, -The Gap,” said a witness who worked at Central Sanitation in July, 1975, including the day Hoffa vanished,  told him that Anthony “Tony Jack” Giacalone visited the facility shortly before Hoffa went missing.

“‘Tony Jack” came in and was walking around calmly, casually, studying the equipment and walking around it for 45 minutes to an hour,” said Tubman. He believes the mob capo was there to inspect where Hoffa’s body was going to go.

And on the evening of July 30, the day Hoffa disappeared, Burnstein said that mobster Anthony “Tony Pal” Palazzolo was also seen at the facility.

“’Tony Pal’ showed up at Central Sanitation in the hours after Hoffa had vanished and basically cleared the place out,” he said.

In addition, Tubman says the employee who operated the massive bundler machine that could have crushed Hoffa’s remains was replaced that afternoon…by a mobster.

“That process would have definitely destroyed any trace of a human body,” he said.

“It was planned, it was programmed, there was a process from the beginning to the end, and when I mean the end, I mean the destruction of the body,” said Richard Convertino, a former federal prosecutor in Detroit, who prosecuted Anthony “Tony Pal” Palazzolo in another case. 

“Tony Pal” was caught on tape years later by an undercover agent boasting that he ran Hoffa’s body through a massive sausage auger in a Detroit meat processing company.

“He said, ‘That’s where I put Jimmy,” said Convertino.

After “Tony Pal” put Hoffa’s body through the auger, the remains were taken to Central Sanitation for disposal, said Burnstein.

The FBI said there was probable cause that Central Sanitation was where Hoffa’s body was destroyed.

Central Sanitation has long been out of business. Seven months after Hoffa disappeared, a fire destroyed the building. It was caused by arson.

The Hoffa case is still active in the Detroit office of the FBI and has a special agent assigned to it.

“The Bureau does take it seriously. It’s still an active investigation,” said Christopher J. Hess, an assistant special agent in charge of the office.

“We continue to follow leads, seek information from the public and make every effort to further the investigation. 

“It’s always my hope that any case that we investigate gets solved and justice is served,” Hess told Fox Nation.

“Certainly in this case, we recognize the historical significance of the case, but more importantly there is a family member and family who still mourns the loss of their family member, in this case Mr. Hoffa, so we hope for information that leads us to the evidence that we need to solve this case.”

“I hope it is solved in my lifetime,” he said.

Even though Hoffa vanished half a century ago, his work continues through the James R. Hoffa Memorial Scholarship Fund, which distributes about $1.4 million a year in scholarship money to the daughters and sons of Teamsters members for their education.

“It’s basically a tribute to what his ideals were and the fact that it helps kids,” said James Hoffa. “It’s part of his legacy… it keeps his memory alive.”

He hopes that his father will not be remembered for what happened to him, but for what he accomplished at the bargaining table and on the picket line over the decades for American workers. Hoffa secured the employee benefits that so many take for granted today, such as higher wages, overtime, increased pensions and health care coverage, he said.

“That’s the memory we want of people, not how he disappeared. You know, one of the things people say sometimes is, it’s not how you died, but now you lived. And you know what? Jimmy Hoffa can look back on that and say, he lived right.”

“We miss him.”

Although no one has been convicted of the Hoffa killing, the Hoffa family wants the truth out, and they say that points to the Detroit Mafia and the Giacalone brothers working with then-Teamsters president Fitzsimmons as those who were responsible.  

Watch all eight episodes of “Riddle, The Search for James R. Hoffa,” streaming on Fox Nation. The final episodes with James P. Hoffa debut on July 30.