Butner, North Carolina – Ted Kaczynski, known as the "Unabomber," who terrorized Americans from 1978 to 1995 with his sporadic, anonymous bombing campaign, has died in prison, US authorities said.

The 81-year-old whose attacks killed three people and injured two dozen, died at the federal prison medical center in Butner, North Carolina, said the Federal Bureau of Prisons.

The reclusive Harvard-educated mathematician, whose targets ranged from academics to random civilians, had a self-professed goal of halting the advance of modern technology and society, mounting his campaign of violence from a shack in rural Montana.

His bombs were either hand-delivered or mailed over nearly two decades, confounding investigators looking to bring him to justice.

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It was only after Kaczynski's capture and the revelation of his identity that the FBI uncovered his previous life – one where he scored 167 on an IQ test and entered university at just 16.

The nickname of "Unabomber" came from his targeting of university professors and airline companies, leading the FBI to dub him the "University and Airline Bomber."

In September 1995, he published his 35,000-word anti-modernity manifesto in The Washington Post, based on a promise that he would stop his bombing campaign if they printed it.

Upon reading it, his estranged brother David thought he might know the author, and alerted the FBI to his suspicions that Ted Kaczynski might be the man they were looking for.

After his arrest in 1996, Kaczynski was convicted to life in prison in 1998. When his lawyers tried to enter a plea of insanity, he asked the court to dismiss them.

Kaczynski plead guilty, which helped him avoid the death penalty.

Long held in a high-security prison in Colorado – one that also held the likes of drug kingpin El Chapo – he was transferred in 2021 to the health center in North Carolina.