It had been a long day on the set of Cover Up, the new CBS-TV series that couples modeling with international intrigue. Jon-Erik Hexum, 26, the high-spirited, impossibly handsome co-star, was bored. Any minute now, barring further delays, Hexum—who played Mac Harper, the ex-Green Beret cum male model lead in the series opposite Jennifer O’Neill—would pick up the .44 Magnum at his side and, as the script demanded, replace the “real” bullets with blanks. As part of a ruse in the plot, he was to pretend to shoot his buddy, played by Mykel T. Williamson.

Jon-Erik leaned back on a bed that was to be used in one of the scenes and dozed off. He woke up a few minutes later, only to discover there was going to be yet another delay. “Can you believe this crap?” he said good-naturedly to workers nearby. Then, before anybody could do or say anything, he raised the gun to his right temple and pulled the trigger. “The whole thing was a joke,” an actor would say later. “It was a tragic sight gag—as if to say, ‘This screwing about is enough to make you want to end it all.’ ”

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The high jinks immediately turned to horror. One crew member ran off the soundstage screaming for help. A station wagon was backed up to the set, and three men carried Jon-Erik’s blood-soaked body into the car. They sped off, their legs dangling out the open tailgate. “I had my hand on his pulse,” said Dino Ganziano, the show’s hairdresser. “It wasn’t the strongest I’ve felt. He was bleeding massively. Another held Hexum’s head, trying to stanch the bleeding with a towel. The third kept his hand in Jon-Erik’s mouth to prevent him from biting his tongue. We were doing a lot of praying.”

It took just a few minutes to cover the mile between 20th Century-Fox Studios and the Beverly Hills Medical Center. When Hexum arrived shortly after 5 p.m. he was comatose and had lost four pints of blood. Surgeons worked over him for five hours. The blast from the blank charge in the .44 Magnum, the most powerful handgun commercially available, had driven a skull fragment the size of a quarter into the center of his brain. “It caused massive hemorrhaging on the right side,” explained Dr. David Ditsworth, 38, the L.A. neurosurgeon who performed the operation, “and the blast effect caused disruption of the remainder of the brain. An injury of this magnitude is virtually always fatal.”

That evening a group of Hexum’s friends, business associates and studio executives clustered in the hospital waiting room, even as the actor’s mother conducted a vigil in the intensive care ward. Al Newman, a studio vice-president, said that Cover Up would continue on the air but the filming of new episodes was “in temporary hiatus.” All were in shock at the sudden end of the promising career of one of Hollywood’s most personable young men. Cover Up already was a medium-size hit. And Hexum had just appeared in his first feature, The Bear, with Gary Busey.

“I only worked with him a brief time,” said Busey, 40. “But it was like jumping on a new trampoline—there was a lot of bounce there. He was what I hope I was like when I first came to Hollywood from Texas. It takes some kind of blind courage to step forth in this business. And he had that.”

Jon-Erik Hexum was born of Norwegian parents in Tenafly, N.J. on Nov. 5, 1957. His father, a chef, left when Jon-Erik was 4. He and his older brother, Gunnar, were reared by their mother, Gretha, who supported the family by working as a secretary by day and a waitress by night. Gretha managed to buy her youngest son a piano and to take him to Broadway musicals. Since there were funds enough for just one ticket, she would wait for him nearby at a coffee shop.

At Tenafly High School, recalls a girlfriend fondly, “He was so totally straight that in the early days everybody thought he was a narc. He was the sort who wore white socks and black shoes until his junior year.” By senior year Jon-Erik was Mr. Everything: He was president of the senior class, master of ceremonies at the Holiday Show, the first boy in the school’s history to become a cheerleader. He acted in school plays and started the school radio station. “He had virtues that seemed to me had no place in the world anymore,” the girlfriend adds. “No one talks about ‘good ambition’ anymore—about making yourself a better person, physically and academically. He worked so hard.” His straightness, however, did not seem to cut into his sense of humor. History teacher John P. Mullin remembers trying to leave the school parking lot one day when Jon-Erik hemmed him in by marching the school band in front of his car.

Jack Hexum, as he was known in those days, subsequently spent a year at Case Western Reserve in Cleveland before moving on to Michigan State, where he majored in social science and worked as a deejay (“Yukon Jack”) at local radio stations.

In his sophomore year he attended his first Michigan State football game and was so smitten that he decided to go out for the team. Although he’d never played high school ball, he made the vaunted Spartans the next year as a “walk-on” flanker. It was at Michigan State that he began to work out with weights, bulking up from 160 to 205 pounds of perfectly proportioned muscle on his celebrated torso. He also renewed his interest in acting. According to theater professor George Schuttler, Jon-Erik showed up one day in his senior year and “kept buttonholing theater faculty and asking how he could become an actor.”

Days after graduation, Jon-Erik arrived in New York. He devoured the trade papers, cultivated casting directors, sent out 300 photos and résumés a week, took a battery of acting lessons and auditioned, auditioned, auditioned for Broadway. To make ends meet he did some modeling, tended bar, even hired out as a domestic. That last job led to the break he needed. “I was working cleaning apartments,” he said last year, “and the guy whose apartment I was cleaning happened to know Bob Le Mond. Evidently this guy saw a lot of talent in the way I cleaned Venetian blinds.”

From Hexum’s point of view, Le Mond held the keys to the kingdom—he was then John Travolta’s manager. At Le Mond’s urging Hexum moved to California in September 1981. Four months later he won the starring role in NBC’s Voyagers!, which got him noticed if not well reviewed. Five weeks after Voyagers! went down the tubes, Jon-Erik landed The Making of a Male Model opposite Joan Collins, one of 1983’s most successful TV movies. Hexum recently recalled the fiery audition in an interview for Playgirl magazine: “We had about five scenes to do and Joan got right into it. We were kissing in front of about 25 people from the studio. I thought, ‘Wow! This is really weird. Holly-wood!’ ” Halfway through the third scene Joan emerged from an embrace with a satisfied smile. Producer Aaron Spelling leaned over and said, “Congratulations,” and sent Hexum off in a limo to shop for $9,000 worth of clothes.

Interestingly, even as Jon-Erik was making inroads into the affections of women all across America, he was repeatedly queried on his sexual preferences. He learned, early on, to deflect his inquisitors with humor. “I certainly wasn’t real confident with girls,” he would say. “I guess that’s what got me started with guys.” Pause. “And small animals.”

If Hexum didn’t date often and openly, it was, he said, because he was utterly absorbed in his career. If he lived first in a dismal little room in Venice with two illegal aliens from Mexico, then in a one-bedroom apartment in industrial Van Nuys and later in an unfurnished house on a less than desirable block in Burbank—so close to the airport he had to pause on the phone between takeoffs—it was, well, because he was saving the more than $200,000 he earned from Voyagers! and the $50,000 he made for Male Model so that he might one day produce his own movies.

“What can I say?” mourned Guy Thomas, Hexum’s personal publicist, after the shooting. “He was just a kid who wanted to be a star.” He was that and more: He was a person of fiber.

One May day last year in Tenafly, high school principal Charles Wilson heard screaming coming from the cafeteria. “My Lord,” he recalls thinking, “there must be a fight in there.” When he went to check, who was it but Hexum! “He’d walked into the cafeteria and created a mob scene,” says Wilson. “I mean, Reggie Jackson came to Tenafly and no one screamed.”

During the same homecoming, Jon-Erik stopped for a visit with his former teacher John Mullin. The talk turned to stunts, which Voyagers! featured in abundance. Hexum explained that the guns used on the show were safe. “They usually take the pin out, or they’re blanks,” he said.

“You can get hurt with blanks,” Mullin admonished.