WASHINGTON (AP) - Theodore "Ted" Kaczynski, known as the “Unabomber,” has died in federal prison, a spokesperson for the Bureau of Prisons told The Associated Press on Saturday.

Kaczynski was found dead around 8 a.m. at a federal prison in North Carolina. A cause of death was not immediately known.

He had been moved to the federal prison medical facility in North Carolina after spending two decades in a federal Supermax prison in Colorado for a series of bombings that targeted scientists.

Kaczynski was serving life without the possibility of parole following his 1996 arrest at the primitive cabin where he was living in western Montana. He pleaded guilty to setting 16 explosions that killed three people and injured 23 others in various parts of the country between 1978 and 1995.