The Unabomber, who terrorized the US in a 17-year bombing spree, died today. In 1996 he was arrested after being turned in by his brother.

• Ted Kaczynski, better known as the Unabomber, was found dead Saturday in his prison cell.
• He was living in a shack in the woods of Montana at the time of his arrest in 1996.
• His brother David turned him in after reading the terrorist's manifesto.

Ted Kaczynski, better known as the Unabomber, died Saturday while serving out four life sentences plus 30 years for running a bombing spree that spanned nearly two decades, killing three people and injuring 23.

Kaczynski was a Harvard-educated mathematician who was living in a shack in the woods of Montana at the time of his arrest in 1996. The tip that ultimately helped the FBI find and arrest Kaczynski came from his very own brother, David.

"I thought he was there because he loved nature and hated technology," David Kaczynki said, back in 2007 when I attended a lecture he hosted at Cornell University.

In 1995, The Washington Post published a 35,000-word manifesto written by the Unabomber, whose real identity at the time remained unknown, about how technology was destroying humanity.

"I felt a kind of chill," David recalled at the 2007 lecture. "And on some intuitive level, I thought, this does sound like Ted."

Here's more from David's lecture, which I covered at the time for The Cornell Daily Sun:

The time following the manifesto's publication was emotionally taxing for David. "We never found anything conclusive," he stated, "for me, it was like a roller coaster. I thought, 'Am I crazy? A suspicion does not make him the Unabomber.'"

Kaczynski remembered Ted as a loving, caring, older brother figure, not a terrorist. He recalled telling himself, "I grew up with this man; is it possible I grew up with evil in my own family but was too blind to see who he truly was?"

Kaczynski recalled seeing himself in a no-win situation due to the threat of capital punishment, constantly asking himself, "What's it going to be like going through life knowing I had my own brother's blood on my hands?"

With hesitation, he decided to alert authorities of his suspicions.

"I cannot tell you how painful it felt…knowing that it could lead my crazy brother to his death," Kaczynski said.

Kaczynski did, however, make the final decision to go to the authorities, which led to Ted's arrest on April 3, 1996. Following the arrest, authorities found a number bombs being built in Ted's cabin, one of which was addressed, intended to be sent to his next victim."

After turning his brother in, David Kaczynski became an anti-death penalty activist and was the executive director of New Yorkers Against the Death Penalty from 2001 to 2012. He later became the executive director of a Tibetan Buddhist monastery in Woodstock, New York, and wrote a memoir in 2016 about his family, entitled "Every Last Tie: The Story of the Unabomber and His Family."