NEW YORK — William Powell was a teenager, angry at the government and the Vietnam War, when he walked into the main branch of the New York Public Library in Manhattan in 1969 to begin research for a handbook on causing violent mayhem.
Over the next months, he studied military manuals and other publications that taught him the essentials of do-it-yourself warfare, including how to make dynamite, how to convert a shotgun into a grenade launcher, and how to blow up a bridge.
What emerged was “The Anarchist Cookbook,” a diagram- and recipe-filled manifesto that is believed to have been used as a source in heinous acts of violence since its publication in 1971, most notably the killings of 12 students and one teacher in 1999 at Columbine High School in Littleton, Colo.
Throughout his manual, Mr. Powell fashioned a knowing voice that suggested broad experience in warfare, sabotage or black ops, mixed with an extremist’s anti-establishment worldview.
“As almost everyone knows, silencers are illegal in virtually all the countries of the world,” he wrote before describing how to build a silencer for a handgun, “but then a true revolutionary believes that the government in power is illegal, so, following that logic, I see no reason that he should feel restricted by laws made by an illegal body.”
He declared that his book was an educational service for the silent majority — not the one identified by President Richard M. Nixon as his middle-American constituency, but the disciplined anarchists who were seeking dignity in a world gone wrong. To them, he offered how-to plans for weaponry and explosives as well as drugs, electronic surveillance, guerrilla training, and hand-to-hand combat — a potent mix that attracted the attention of the FBI.
The book also attracted a big audience. More than 2 million copies have reportedly been sold, and more have been downloaded on the internet.
“It was inevitable that he did it,” James J.F. Forest, a professor of security studies at the University of Massachusetts Lowell, said in a phone interview. “If he hadn’t done it, somebody else would have. It’s human behavior to tap into a dangerous stream of knowledge, and in his case, he was inspired to make that dangerous information available to anyone else who was interested.”
Mr. Powell never revised the book or wrote a sequel, but his original stayed in print, through Lyle Stuart and its successor company, Barricade Books, and most recently by Delta Press.
Eventually, he renounced the book. In 2000, he posted a statement to that effect on Amazon.com. And later, in 2013, he expressed his regret in an article he wrote for The Guardian.
He chose a career as a teacher, specializing in working on behalf of children with special needs.
And then, on July 11 of last year, he died of a heart attack while vacationing with his family near Halifax, Nova Scotia. He was 66 and had lived part time in Massat, France, when he was not working with his wife, Ochan, on educational projects in other countries.
His family reported the death on Facebook, but few if any obituaries followed. His son Sean said that the people who needed to know had been told and that the family had not thought of reaching out to newspapers.
It was not until last week that his death became more widely known, with the theatrical release of “American Anarchist,” a documentary about Mr. Powell. His death was noted in the closing credits.
The director, Charlie Siskel, said he had interviewed Mr. Powell over a week in 2015.
“What interested me was: How do you go through 40 years of your life with his dark chapter in the background?” Siskel said Monday. “How does one sleep at night or get through the day?”
On camera, Mr. Powell seemed to struggle to absorb the idea that his book had apparently had an influence on a number of notorious criminals. One was Zvonko Busic, a Croatian nationalist who hijacked a TWA flight in 1976 while carrying phony bombs after leaving a real one at Grand Central Terminal that killed a police officer who tried to deactivate it.
Others included Thomas Spinks, who was part of a group that bombed abortion clinics in the 1980s; Timothy McVeigh, who bombed the Alfred P. Murrah Federal Building in Oklahoma City in 1995; Eric Harris, one of the Columbine attackers; and Jared Loughner, who killed six people during his attempted assassination of Representative Gabrielle Giffords in Arizona in 2011.
“When ‘The Cookbook’ has been associated with Columbine and the later characters and killing, I did feel responsible, but I didn’t do it,” Mr. Powell told Siskel, adding: “Somebody else with a perverted, distorted sense of reality did something awful. I didn’t.”