Theodore “Ted” Kaczynski, the Harvard-educated mathematician known as the Unabomber, was found dead in his cell at the age of 81.

Kaczynski, who spent 17 years carrying out a bombing campaign that resulted in the deaths of three people and injuries to 23 others, was found unresponsive in his cell at the federal prison medical center in Butner, North Carolina, and was pronounced dead on Saturday morning.

Kaczynski earned his notorious nickname from the FBI and had been held at the federal Supermax prison in Florence, Colorado, since May 1998. He was serving four life sentences plus 30 years for his acts of terror that targeted universities across the country. Kaczynski admitted to carrying out 16 bombings between 1978 and 1995, leaving some victims permanently maimed.

The impact of Kaczynski’s homemade bombs reverberated throughout society, leading to changes in package handling and airport security measures. In July 1995, his actions even caused disruptions to air travel on the West Coast.

The publication of Kaczynski’s 35,000-word manifesto, titled “Industrial Society and Its Future,” was a pivotal moment in his capture. After The Washington Post, in collaboration with The New York Times, made the difficult decision to publish the manifesto in September 1995, Kaczynski’s brother David and sister-in-law Linda Patrik recognized the writing style and alerted the FBI. The manifesto, which expressed Kaczynski’s views on modern society and technology, ultimately led to his identification and arrest.

Kaczynski’s capture exposed him as a reclusive individual living in a small cabin in the Montana wilderness. Although some initially romanticized him as an anti-hero, the reality of his isolated and vengeful nature emerged.

In his own writings, Kaczynski admitted to acting out of a desire for revenge rather than a commitment to any ideological cause. A psychiatric evaluation conducted in prison diagnosed him as a paranoid schizophrenic, highlighting his belief in persecution by family members and society.

Kaczynski vehemently rejected any notion of mental illness and attempted to prevent his lawyers from pursuing an insanity defense during his trial. He eventually pleaded guilty, maintaining his sanity and stating that he did not experience delusions.

Despite the infamy surrounding his acts, Kaczynski’s intellect was widely acknowledged. He had attended Harvard at the age of 16, published papers in respected mathematics journals, and crafted sophisticated bombs concealed within handmade wooden boxes.

The Unabomber primarily targeted universities and airlines, with his attacks leaving a lasting impact on the public’s perception of safety and security. While his reign of terror ended in 1995, the scars from his bombings and the loss suffered by the victims and their families remain.

Historian Alston Chase uncovered in 2003 that Kaczynski reportedly took part in the classified Harvard experiment MK-Ultra for almost three years.

Kaczynski’s death marks the end of a chapter in American criminal history, but his legacy as a remorseless killer driven by personal grievances will not be forgotten.