Kaczynski was found dead around 8 a.m. in a federal prison in North Carolina.
At the moment the cause of his death is unknown. He was serving a life sentence without bail after his 1996 arrest in a rudimentary cabin where he lived in western Montana. He pleaded guilty to triggering 16 explosions that killed three people and injured 23 others in various parts of the country between 1978 and 1995. He spent two decades in a Supermax prison in Colorado for a series of bomb attacks on scientists.