NEW YORK (AP) — Jack Ketchum, a prize-winning horror and screenplay writer known for fiction such as “The Box” and the controversial “Off Season,” and once labeled by Stephen King as likely the scariest writer in America, has died. He was 71.

Ketchum’s friend and webmaster Kevin Kovelant told The Associated Press that Ketchum died Wednesday morning. No other details were immediately available. Jack Ketchum is the pen name for Dallas Mayr, who initially wrote as “Jerzy Livingston.”

“Very sorry to hear that an old friend of mine, Dallas Mayr, died,” King tweeted Wednesday. “He terrified readers with books like OFF SEASON and THE GIRL NEXT DOOR. Dallas and I went back to the 70s together.”

Ketchum, whose admirers include King and Chuck Pahlaniuk, was a Newark, New Jersey, native and Emerson College graduate. As a young man, he worked as a short order cook, actor, playwright and teacher, and for a time he was the literary agent for “Tropic of Cancer” author Henry Miller. He had always loved scary stories and in his teens was mentored by Robert Bloch, whose novel “Psycho” was the basis for the Hitchcock film.

He won several prizes for horror and his books also were a source for filmmakers, including “The Girl Next Door” and “The Lost.” He made an impression right away. His first novel, the cannibalistic “Off Season,” was so violent that publisher Ballantine pulled back on support. The 1980 book has been republished over the years, most recently in 2015.

“Jack Ketchum’s first novel … set off a furor in my supposed field, that of horror, that was unequaled until the advent of Clive Barker,” King said in 2003 upon accepting an honorary National Book Award. “It is not too much to say that these two gentlemen remade the face of American popular fiction.”