After the anonymous Unabomber demanded in 1995 that his manifesto, "Industrial Society and Its Future," be published in a major newspaper as a condition for ceasing his mail-bomb campaign, the New York Times and the Washington Post both published the manifesto, hoping somebody would recognize the writing style of the author.
David's wife Linda Patrik first suspected Theodore and urged David to read the manifesto when it was published. David recognized Ted's writing style, and the experienced criminal defense lawyer the couple found notified authorities. On April 3, 1996, police arrested Ted Kaczynski in his rural shack in Lincoln, Montana. David had received assurance from the FBI that his identity as the informant would be kept secret, but his name was leaked to the media. In addition, he sought a guarantee from federal prosecutors that Ted would receive appropriate psychiatric evaluation and treatment. The Justice Department's subsequent active pursuit of the death penalty for Ted and Attorney General Janet Reno's initial refusal to accept a plea bargain in exchange for a life sentence was seen as a betrayal by David and other Kaczynski family members. Such a plea bargain eventually resulted, and Ted was sentenced to serve life imprisonment with no possibility of parole. David has said in broadcast interviews since his brother's arrest, that notifying federal authorities of his brother's possible involvement in the Unabomber case was a painful decision. But he felt morally compelled to do it in order to save lives that might have been taken had the bombings continued. David received the $1 million reward the FBI had offered for the Unabomber's capture; he donated most of the money to the families of his brother's victims and used the rest to pay off his legal expenses.
David was assistant director of the Equinox shelter for runaway and homeless youth in Albany, where he counseled and advocated for troubled, neglected and abused youth in the Capital District. His experience of having his brother confront the death penalty later motivated David to become an anti-death penalty activist. In 2001, David Kaczynski was named executive director of New Yorkers Against the Death Penalty (as of 2008 New Yorkers for Alternatives to the Death Penalty). While the mission of NYADP originally focused only on ending the death penalty, under David's guidance, in 2008, it broadened its mission to address in a progressive manner the unmet needs of all those affected by violence, including victims and their families. In 2012, David was appointed executive director of Karma Triyana Dharmachakra, a Tibetan Buddhist monastery located in Woodstock, NY.
Kaczynski is a graduate of Columbia College of Columbia University. He is also a practising Buddhist and is a vegetarian. In 2009 he published an essay about his relationship with his brother Ted, from childhood to adulthood, which appeared in a collection of essays.
- "New Yorkers Against the Death Penalty New Yorkers Against the Death Penalty". Albany, New York: New Yorkers for Alternatives to the Death Penalty. Retrieved 2009-03-30.
- AOL News
- New York Times
- Interview on WXXI (AM), Rochester, NY, March 13, 2002.
- Matthew Purdy (August 5, 2001). "Our Towns; Crime, Punishment and the Brothers K.". New York Times. Retrieved 2009-03-30.
- Andrew Blauner, ed. (2009-04-20). Brothers: 26 Stories of Love & Rivalry. Jossey-Bass. ISBN 0-470-39129-4.