'The Unabomber's ego may have led to his downfall': The serial killer unmasked by his own writing

The Unabomber's campaign of violence had baffled investigators for almost two decades. The BBC reported on his arrest 30 years ago when the "brilliant" mathematician "laid a trail to his own front door".

On 3 April 1996, US federal agents surrounded a remote log cabin in the Montana woods and led out Theodore "Ted" Kaczynski, a dishevelled figure who until then had existed in the public mind only as a hooded man in dark glasses from a "wanted" poster sketch. For almost 18 years, the Unabomber was one of the US's most wanted criminals, a mystery man whose primitive parcel bombs were mailed with no clear motive or regular pattern.

What finally trapped him was his own writing. Two major American newspapers agreed to publish his anti-technology manifesto if he promised not to kill again. His distinctive words were first identified by his brother's wife, whom he had never even met. As BBC Newsnight's Krishnan Guru-Murthy noted, "The academic who dropped out to live in a primitive cabin had laid a trail to his own front door."

The search for the Unabomber began in May 1978 when a primitive homemade bomb was mailed to Northwestern University in Illinois, followed by a second attack almost a year later. In November 1979, an altitude-triggered bomb he had mailed went off aboard an American Airlines flight. While it did not work as intended, 12 people were treated for smoke inhalation.

Because his targets seemed to be universities and airlines, the FBI came up with the code name UNABOM. Over the following years he used increasingly sophisticated bombs to attack a further 13 times, killing three people: computer rental shop-owner Hugh Scrutton, advertising executive Thomas Mosser and timber industry lobbyist Gilbert Murray.

As his targets were essentially random, and his bombs were built from common items such as pieces of wood and lamp cords, investigators were working with little more than scraps. FBI chief ballistics investigator Chris Ronay dubbed him the "recycle bomber". He told the BBC in 1996: "He's rummaging through trash cans and used-materials bins and finding things that he can then create like a Neanderthal."

To justify his violence, in April 1995 the Unabomber sent the New York Times and Washington Post a 35,000-word academic diatribe titled Industrial Society and its Future. In the essay, he argued that modern life eroded human freedom and dignity, and claimed that only dismantling technological systems could prevent further psychological and social harm. He offered to stop killing people if the screed was published by the two most prestigious newspapers in the country. Washington Post publisher Donald Graham told the BBC in 2016: "The initial anxiety was obvious. If you succumb to this demand and agreed to print this document, might it trigger other demands to print other such documents?"

FBI special agent Terry Turchie told the BBC that investigators initially thought it would be a bad idea to publish the manifesto "because it was just too far out there", but then they had a rethink. They reasoned that if the manifesto were published, someone would almost certainly recognise the voice behind it "because these words are so passionate". After three months of agonising, on........

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