William Diehl, the best-selling author known for “Sharky’s Machine” and “Primal Fear” — fast-paced thrillers that became box-office hits — died Friday in Atlanta. He was 81.

Diehl was a former journalist and photographer who became a novelist late in life, after a dispirited awakening at his 50th-birthday party. Over the next three decades he wrote nine novels that appealed to popular tastes with plot lines fueled by murder, greed, romance and other forms of mayhem.

He was believed to be nearly finished with his 10th novel when he was hospitalized last week. It is titled “Seven Ways to Die.”

Diehl, a native of Jamaica, N.Y.,often cited his experiences during World War II as a strong influence on his fiction. He lied about his age to join the Army Air Corps at 17 and served as a ball turret gunner on a B-24 during World War II. His conduct in that job earned the Distinguished Flying Cross, Purple Heart and Air Medal with three Oak Leaf Clusters.

Even without World War II, Diehl’s life was more eventful than most. According to family lore, Mae West was his baby sitter once, before she became a Hollywood sex symbol. On a school field trip in 1937, he witnessed the explosion of the Hindenburg, then the world’s largest aircraft.

After the war, he graduated from the University of Missouri with a degree in creative writing and history and in 1949 moved to Atlanta, where he joined the staff of The Atlanta Constitution as an obituary writer. He worked as a reporter and columnist. He then became a photographer for the Unites States Information Agency. In 1967, while documenting Martin Luther King Jr.’s tour of Mississippi, he had his throat slashed by two men armed with a straight razor.

The turning point of his life came in a moment characterized more by bathos than pathos, however.

He had no permanent job and was on his second marriage in 1974 when he turned 50. Someone had given him a party with an ice-cream cake shaped like a typewriter, an allusion to Diehl’s long-held dream of becoming a novelist. The cake, too pretty to eat, melted into a gooey mess, which struck Diehl as a metaphor for his life.

“I’d been working for 30 years, and what did I have to show for it?” he thought when he beheld the cake.

The next day, he sold all his cameras, borrowed $5,000 from his best friend and resolved to launch his best and final career.

While on jury duty some time later, he hatched the plot of “Sharky’s Machine” (1978), which races around the globe from Italy to Hong Kong to Atlanta, where a detective stumbles into a complex web of extortion, sex and murder. Critics handed it raves. It was turned into a successful 1981 movie directed by Burt Reynolds, who also starred as Sgt. Tom Sharky. In a cameo role as a pimp who punches out a hooker in a jail cell, Diehl broke his finger.

“Primal Fear” followed a similar trajectory from best-seller lists to big screen, where Richard Gere and Edward Norton starred in the 1996 film..

Some reviewers complained that Diehl’s characters were not well developed and that the writing was clunky. “His sentences crawl across the page and die,” John Coyne wrote in the Washington Post.

His last published novel was “Eureka,” which came out in 2002. Somewhat of a departure from his earlier works, it is a historical thriller that covers the first four decades of the 1900s. In a starred review, Publishers Weekly called it “his best novel ever.”

He concocted the violent scenarios in most of his books in the placid environs of Georgia’s St. Simon’s Island, where he lived for 20 years with his third wife, Virginia Gunn, a former Atlanta television reporter.