By Peter Castro
April 28, 1997 12:00 PM

BILLY BOB THORNTON THOUGHT that the hard times were behind him. Sixteen years after arriving in Hollywood from rural Arkansas as a penniless and desperate actor, he turned his life—and his fortune—around by directing, starring in and winning an Oscar for writing Sling Blade, the tale of a slow-witted man who wrestles with questions about life and morality after being released from a mental institution.

But Thornton’s sudden stardom lost some of its luster last week following reports that his wife of four years, Pietra Dawn Thornton, 27, had filed for divorce on April 11, citing irreconcilable differences. The fourth Mrs. Thornton, who on March 24 had sat beamingly by her husband’s side at the Academy Awards, also asked a state judge for a restraining order against the 41-year-old actor. “Over the past year, at least once or twice per month, [Thornton] has hit me, pushed me, punched me, bit me or otherwise physically attacked me, sometimes in front of the children [William, 3, and Harry James, 2],” Pietra says in court papers. She adds that around the time of the Oscars, Thornton “lifted me off the ground by my neck and said, ‘I’m going to kill you, and then I’m going to go to prison and the children will be orphans.’ ”

Thornton vehemently denies the charges. “I’m sorry that Pietra’s advisers have convinced her to take this malicious and untruthful course of action by making these false accusations of physical and mental abuse,” he said in a prepared statement. “Our marriage was not perfect, but I never exhibited the behavior she’s accusing me of. Our concerns right now should be about our sons, who will suffer the most as a result of her advisers’ conduct.”

Thornton, who has moved out of the couple’s three-bedroom Pacific Palisades home (child-visitation rights have yet to be determined), will have a formal chance to respond during a May 5 court hearing. One thing that already seems certain is that the case will center on Pietra’s abuse charges and not on rumors that Thornton was involved with actress Laura Dern, whom he met last month while both were working as guest stars on the coming-out episode of ABC’s Ellen. Through his publicist, Billy Bob dismisses the alleged affair as nonsense. Meanwhile, Pietra says that apart from her personal safety, her main motive in leaving Thornton is to prevent their sons from becoming “wife abusers or violent people.”

Thornton’s previous marriages all had their rocky stretches. In 1978 he wed fellow Arkansas resident Melissa Lee Gatlin, with whom he had a daughter, Amanda, now 17. Gatlin filed for divorce in 1980, later citing “incompatibility and adultery on his part.” In 1986, Thornton, then 30 and struggling in L.A., married actress Toni Lawrence, but the couple split the following year with Lawrence filing for divorce in 1988. “He’s really talented, that’s obvious now,” says Lawrence, a potter who has remarried and is living in L.A. “But,” she adds, declining to elaborate, “he’s very troubled.”

Thornton’s third marriage, to Cynda Williams, his costar in the film One False Move, shot in 1990, lasted less than a year, ending in 1992. (“We were just friends; we had no business being married,” Thornton told PEOPLE.) But Thornton was certain he’d found his soulmate in Pietra, whom he met outside an L.A. Italian restaurant that same year. Pietra herself told PEOPLE last February that “my girlfriends would die to have a man this intelligent and this wonderful.” And as a husband, she said, he “would never do anything to make me question the integrity of our marriage.”

Her abrupt about-face has surprised many of their friends. “I never saw him speak to her in any kind of abusive manner,” says a pal of Thornton’s. “Everybody was shocked.” Not exactly everyone. “Billy Bob, I love him to death,” says Natalie Canerday, who played the abused woman he defends in Sling Blade. “I’d give him a kidney, but he’s just not the marrying kind. There are just some boys who are better friends than husbands.”