Between 1978 and 1995, Kaczynski, 81, killed three people and injured 23 others in a mail-bombing spree. He eventually pleaded guilty to his offenses.

After escaping capture for over 20 years, he was sentenced to life in prison without the possibility of release in 1996.

The Harvard-educated mathematician was apprehended in a Montana cabin.

He was a man who captivated Americans for decades, and he was the subject of countless television documentaries.

Kaczynski has spent the last three decades in prisons throughout the United States, most recently in the Federal Medical Center in Butner, North Carolina.

A spokeswoman for the US Bureau of Prisons told the BBC that prison guards discovered Kaczynski’s body on Saturday morning about 00:25 local time (04:25 GMT).

It was not immediately obvious what caused his death.

“Responding staff immediately initiated life-saving measures,” according to the spokeswoman. After that, Kaczynski was “transported by EMS to a local hospital and later pronounced deceased by hospital personnel.”

Prior to being transferred to the facility in December 2021 due to poor health, he had been incarcerated at the federal Supermax prison in Florence, Colorado, since May 1998.

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4th Archives: The Unabomber Kaczynski’s violent campaign rocked the United States, permanently maiming a number of his victims and changing the way Americans sent letters.

His crimes were revealed after he compelled the Washington Post and the New York Times to publish his rambling and rage-filled diatribe, Industrial Society and Its Future, in September 1995.

They agreed to issue the manifesto on the advice of the FBI and the US attorney general after Kaczynski threatened to cease his campaign if his treatise was published in a major newspaper.

The 35,000-word anonymous document railed against modern living, claiming that technology was causing Americans to feel alienated and powerless.

However, after reading the papers, Kaczynski’s brother and sister-in-law recognized the tone and notified the FBI, which had been searching for him for years in the country’s longest manhunt.

Authorities apprehended him in a 10-by-14-foot (3-by-4-metre) plywood and tarpaper home in Lincoln, Montana, in April 1996.

The shack included journals, a coded diary, explosives, and two finished bombs.

While many found Kaczynski’s manifesto to be openly political in tone, he never attempted to embrace the revolutionary mantle that others attributed to him.

In his notebooks, he stated that he did not pretend to be a “altruist or to be acting for the ‘good’ (whatever that is) of the human race,” but rather that he acted “merely from a desire for revenge.”

His misdeeds appeared to begin immediately after his brother sacked him from the family firm for sending abusive limericks to a female colleague who had dumped him after two dates.

From there, he retired to the Montana wilderness and his hand-built cottage, which lacked heating, plumbing, and electricity.

His initial strikes were directed at Northwestern University in Illinois. The two bombings, which occurred nearly a year apart on May 25, 1978 and May 9, 1979, injured two individuals.

Then, in November 1979, an altitude-triggered bomb delivered to him detonated aboard an American Airlines flight. Smoke inhalation caused the deaths of twelve persons.

The FBI dubbed him the Unabomber after his early attacks, which looked to target institutions and aircraft.
He attacked 13 more times in the years that followed, killing three people: computer rental company owner Hugh Scrutton, advertising executive Thomas Mosser, and forestry industry lobbyist Gilbert Murray.

Mr Mosser’s wife testified at Kaczynski’s trial that her husband was killed on the day he was meant to pick up a Christmas tree with his family and described the minutes after the attack.

“He was moaning very softly,” she remarked, referring to her spouse. “His right hand’s fingers were dangling. I took his left hand in mine. I informed him that assistance was on its way. I told him how much I adored him.”

Kaczynski’s reasons have been the subject of continuous discussion since his imprisonment.

He had an IQ of 167 when he was a youngster, and he skipped two grades to join Harvard University at the age of 16.

He was described as “a twisted genius who aspires to be the perfect, anonymous killer” by FBI agents, and he was diagnosed as a paranoid schizophrenic by a doctor who interviewed him in prison.

Sally Johnson said in a 47-page report that the manifesto’s “central themes” “involve his belief that he is being maligned and harassed by family members and modern society.”

But Kaczynski argued that he knew exactly what he was doing, and he attempted suicide in prison after his legal team tried to submit an insanity plea.

In a 1999 interview with Time magazine, he stated that he did not suffer from “delusions and so on and so forth.”

“I’m confident in my own sanity,” he remarked.