Kaczynski, who made and sent many of his bombs while living in a primitive cabin with no running water in rural Montana, was found unresponsive at a facility for prisoners with special health needs, in North Carolina, and pronounced dead at a local hospital on Saturday.
The Harvard University graduate, a loner since childhood, targeted academics, scientists and computer store owners and even tried to blow up a commercial airliner in a one-man terror campaign from 1978 to 1995 against what he believed were the evils of modern technology.
For years, he baffled police who dubbed his case UNABOM, for University and Airline Bombings. A breakthrough came when Kaczynski released a rambling, 35,000-word manifesto entitled "Industrial Society and Its Future" that was published in the media in September 1995.
Kaczynski's younger brother, David, tipped off police that the author's ideas sounded like those of Ted. Agents arrested the dishevelled Unabomber at his cabin in April 1996.
After rejecting his lawyers' attempts to have him plead insanity, Kaczynski pleaded guilty to all federal charges relating to the bombings in 1998 and a California court sentenced him to four life terms plus 30 years in prison.
Described by the FBI as "a twisted genius", it is not known exactly what caused Kaczynski to channel his talent toward evil.
However, his participation in an infamous science experiment at Harvard may have been one reason
There, psychologists subjected volunteer students, including Kaczynski, to hours of extreme verbal and emotional abuse as part of an attempt to measure how people handled stress. The experiment, now regarded as unethical, lasted three years.
Others have cited a period in Kaczynski's childhood when he spent long periods in isolation due to a severe outbreak of hives.
Kaczynski was assistant mathematics professor at the University of California at Berkeley before resigning and moving to Montana in 1971 where he bought land and built a cabin.
The cabin served as the main base for his homemade bombing campaign, which began in 1978 when he left a package for an engineering professor at Chicago's Northwestern University. A police officer and a graduate student were injured.
Kaczynski took aim at a bigger target in 1979, placing a bomb in in the hold of an American Airlines plane that gave off smoke on a domestic flight, forcing an emergency landing.
In 1980, Kaczynski sent a package bomb that exploded and injured United Airlines President Percy Wood at his Illinois home.
His first fatal victim was computer store owner Hugh Scrutton, 38, who died when a bomb loaded with nails and splinters went off in the parking lot of his store in Sacramento, California in 1985.
As his bombs became more sophisticated, Kaczynski also killed New Jersey advertising executive Thomas Mosser, who had worked on improving the public image of oil major Exxon, with a mail bomb in 1994.
He then murdered Gilbert Brent Murray, head of a California timber industry lobbying group, with a mail bomb in 1995.
In all, the Unabomber set off 17 bombs, injuring around 25 people, some of whom lost vision, hearing or fingers.
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