The term Unabomber, is made up of the letters: university, airline, bomber, as Kaczynski targeted these institutions in his bombing campaign.

Over 18 years, Theodore John Kaczynski sent 16 mail bombs, killing 3 and injuring 23. He was arrested at his Lincoln, Montana home on this day.

He had became a professor at the University of California but cut short what looked set to become a brilliant career in 1969.

In 1971 he set up home in Montana. Here he became something of a hermit and wrote a number of academic papers highlighting the dangers of technology. It is believed that his failure to get one of his earlier papers published led to the first mail bombs in 1978.

He was eventually caught after his brother recognized some of his writings. The Washington Post agreed to print the 35,000 word Unabomber's Manifesto after Kaczynski said he would stop his campaign if it were published.

At Kaczynski home, police found a live bomb and an original copy of the manifesto.

On January 22 1998 Kaczynski plead guilty to all charges and was spared the death penalty. He was sentenced to four life sentences plus 30 years.