"He had scored 167 on an I.Q. test as a boy and entered Harvard at 16. In graduate school, at the University of Michigan, he worked in a field of mathematics..."

"... so esoteric that a member of his dissertation committee estimated that only 10 or 12 people in the country understood it. By 25, he was an associate professor at the University of California, Berkeley. Then he dropped out — not just from Berkeley, but from civilization. Starting in 1971 and continuing until his arrest, he lived in a shack he built himself in rural Montana. He forsook running water, read by the light of homemade candles, stopped filing federal tax returns and subsisted on rabbits."

From "Ted Kaczynski, ‘Unabomber’ Who Attacked Modern Life, Dies at 81/Alone in a shack in the Montana wilderness, he fashioned homemade bombs and launched a violent one-man campaign to destroy industrial society" (NYT).

ADDED: The story at the link has been updated. It now gives a cause of death — suicide — based on "three people familiar with the situation." It also reflects on the soundness of ideas in the manifesto — as seen today:

His manifesto accorded centrality to a healthy environment without mentioning global warming; it warned about the dangers of people becoming “dependent” on technology while making scant reference to the internet. To young people afflicted by social media anomie and fearful of climate doom, Mr. Kaczynski seemed to wield a predictive power that outstripped the evidence available to him.

In 2017 and 2020, Netflix released documentaries about him. He maintained postal correspondence with thousands of people — journalists, students and die-hard supporters. In 2018, Wired magazine announced “the Unabomber’s odd and furious online revival,” and New York magazine called him “an unlikely prophet to a new generation of acolytes.”
Becoming ‘the Unabomber’

If you click on my "Kaczynski" tag, you'll see that in 2015, I posted about the manifesto and said:

Ted had a lot to say about leftists in his manifesto. Let's look. It's worth reading if only to see how surprisingly similar it is to things you may be seeing every day on the internet....

I have some long quotes from the manifesto, including: "The two psychological tendencies that underlie modern leftism we call 'feelings of inferiority' and 'oversocialization.'"