Ted Kaczynski, better known as the "Unabomber," was found dead in his prison cell on Saturday morning. 

The 81-year-old Kaczynski, according to the Associated Press, was being kept at a federal prison medical center in Butner, North Carolina.

The outlet - citing Kristie Breshears, a spokesperson for the federal Bureau of Prisons - reports, "he was found unresponsive in his cell early Saturday morning and was pronounced dead around 8 a.m."

At the time of this writing, a cause of death was not announced. ABC 13, however, reports that Kaczynski's death is being investigated as a suicide.

Who was he?

Kaczynski was a Harvard-educated mathematician who is better known for the deadly bombings that he carried out.

Fox News reports:

 Kaczynski sent deadly handmade bombs by mail targeting those he believed were causing the destruction of nature through technological advancement. His campaign of terror — which included the bombing of an American Airlines flight with an altitude-triggered device — changed how Americans sent packages through mail and boarded airplanes.

Kaczynski got the name the "Unabomber" from the FBI. The FBI gave him that name, according to Fox, because his early targets appear to be airlines and universities.

The bombings went on for nearly two decades, from the late 1970s to the mid-1990s. During that time, authorities failed to locate the bomber.

It wasn't until Kaczynski forced the Washington Post, in 1995, to publish his manifesto that the FBI got on to Kaczynski's trail. And, this was because the agency received a tip from Kaczynski's family members, who recognized his writing style.

Finding Kaczynski

All-in-all, it took authorities some 17 years to locate Kaczynski. At the time, the manhunt was the longest and costliest in U.S. history. Kaczynski was finally found in 1996 living in a primitive cabin in western Montana.

After his arrest, Kaczynski pled guilty to killing three people and injuring nearly two dozen others as the result of 16 bombings that he carried out between 1978 and 1995. Upon arresting Kaczynski, the authorities actually found two complete bombs in his possession, suggesting that further bombings may have been prevented.

For his crimes, Kaczynski was sentenced to life imprisonment without the possibility of parole. This was the sentence that he was serving at the time of his death.

Kaczynski served the majority of this sentence at the federal Supermax prison in Florence, Colorado. He was moved to the medical facility in North Carolina in December 2021.

It is unclear when or if the cause of Kaczynski's death will be released.