Theodore 'Ted' Kaczynski, known as the 'Unabomber,' has died in federal prison

Theodore Kaczynski looks around as U.S. Marshals prepare to take him down the steps at the federal courthouse to a waiting vehicle on June 21, 1996, in Helena, Mont. A spokesperson for the Bureau of Prisons told The Associated Press that Kaczynski, known as the “Unabomber,” has died in federal prison. The cause of death was not immediately known. (AP Photo/Elaine Thompson, File)

Theodore “Ted” Kaczynski, the Harvard-educated mathematician who retreated to a dingy shack in the Montana wilderness and ran a 17-year bombing campaign that killed three people and injured 23 others, died Saturday. He was 81.

Branded the “Unabomber” by the FBI, Kaczynski died at the federal prison medical center in Butner, North Carolina, Kristie Breshears, a spokesperson for the federal Bureau of Prisons, told The Associated Press. He was found unresponsive in his cell early Saturday morning and was pronounced dead around 8 a.m., she said. A cause of death was not immediately known.

Before his transfer to the prison medical facility, he had been held in the federal Supermax prison in Florence, Colorado, since May 1998, when he was sentenced to four life sentences plus 30 years for a campaign of terror that set universities nationwide on edge. He admitted committing 16 bombings from 1978 and 1995, permanently maiming several of his victims.