The man known as the “Unabomber” has been transferred to a federal prison medical facility in North Carolina after spending the past two decades in a federal Supermax prison in Colorado for a series of bombings that targeted scientists.

A U.S. Bureau of Prisons spokesperson said Thursday that 79-year-old Theodore Kaczynski was moved Dec. 14 to the bureau's Butner medical center in eastern North Carolina.

A spokesperson declined to disclose any details of Kaczynski’s medical condition or the reason for his transfer.

The Harvard-trained mathematician is serving life without the possibility of parole after pleading guilty in 1998 to setting 16 explosions that killed three people and injured 23 others in various parts of the country.