The Unabomber, Ted Kaczynski, the US mailing system and security protocols during airplane boarding in the country|Public Domain

A lone bomber who terrorized the nation for nearly 20 years, Ted Kaczynski, aka Unabomber, was found dead in his prison cell Saturday. Authorities confirmed he was found unresponsive.

He was 81 and suffering from late-stage cancer. The AP reported that he died by suicide.

Kaczynski killed three and injured 23 others during a mass bombing spree between 1978 and 1995 using mail pipe bombs, which he made at his home in Montana.

His nickname, Unabomber, was coined by the FBI because he targeted airlines and universities. Till before his arrest, many Americans were afraid to even go through their mail.

Kaczynski attended Harvard University at the age of 16 and even taught at the University of California, Berkeley.

He felt society was falling victim to technology and causing environmental calamity, which needed to be addressed through terror attacks. He came to believe that humans were slaves to machines.

His homemade bombs were usually delivered as parcels. His brand of terror forever changed the US mailing system and security protocols during airplane boarding in the country.

Kaczynski was caught by the FBI in 1996, almost a year after the New York Times and Washington Post published his 35,000-word manifesto at the FBI’s request.

His brother and sister-in-law recognized his style of writing and informed the authorities.

Ted Kaczynski was diagnosed as a paranoid schizophrenic by the prison psychiatrist, a diagnosis which he denied and pleaded guilty to his crimes. He was awarded four life sentences plus 30 years for a campaign of terror.