Nobody here will ever know for sure what possessed Sonny Hammett when he shot four of his bosses to death inside the Anchor Glass Container Corp., wounded a fifth supervisor, then pressed his .38-cal. Smith & Wesson revolver to his chest and killed himself.

Mansel (Sonny) Hammett, 39, who worked in the giant glass-making plant for 18 years, killed his bosses two hours after he was suspended, sent home and threatened with firing for defying company orders by talking to his wife, Judith, who worked on the same shift at the southwestern Pennsylvania plant.

The murder-suicide nearly three weeks ago at Fayette County's largest employer has torn this factory town of 2,500 and sparked bitter debate over whether assembly-line pressure and fear of losing his job may have pushed Hammett to the brink.

In bar rooms, at church services, in news stories and in tidy working-class homes, there are accusations that company discipline drove him crazy. The theory is dismissed by those who say that workplace pressures are universal.

"I guess nobody really likes their boss, so it's human nature to talk about the pressures they create," said Mayor David H. Goldblum, a school administrator who was pressed into service taking statements from witnesses at the scene.

Goldblum said most workers he interviewed blamed workplace pressures for Hammett's behavior. "You can put the blame on a lot of things, but the person who went to his grave is the only one who will ever know the truth," he said.

The Rev. Michael Bucci, pastor of St. Rita's Roman Catholic Church, where many of Anchor's 600 workers worship, called Hammett "a victim of our times . . . . We are living in very uncertain times, especially where jobs are concerned," he said on the Sunday after the killings.

Borough councilman Tom Duncan cited larger industry problems: "The foreign imports put pressure on management of the corporation, who in turn puts pressure on the local management, who then are forced to put the pressure on the workers . . . ."

Hammett's fellow members of the Glass, Pottery, Plastics and Allied Workers Union charged that layoffs, work speedups and heavy-handed rules helped trigger his frenzy -- a contention the company rejects. "There was tension in the plant," local union president John Kaylor said on the day of the shootings. "They were asking us to do things that a human being cannot do for eight hours a day."

"It's a pressure cooker in there," said a coworker of Hammett, Jerry Jacquillard, citing increased workloads and disciplinary threats. "When we took breaks, people sometimes talked about how somebody someday was gonna go over the edge and start shooting," he said. "We actually talked about somebody coming in there with a gun someday. We just didn't know who or when."

But Anchor's vice president and general counsel, Richard Everett, disputed the speculation that job stress was to blame. "In every job there's a certain amount of stress . . . ," he said. "We just don't know and perhaps will never know what caused such a terrible tragedy."

Noting that the United States has fewer than 100 glass plants -- having lost 15 in the last three years -- Everett said, "We have made great strides in productivity and quality. It's a measure of that progress that South Connellsville is still operating. It's a tribute to the cooperation of unions and management."

After the Saturday slayings, the company reopened for the Sunday afternoon shift, making bottles for soda, beer, whiskey and baby food in a competitive industry jeopardized by foreign competition and plastics.

Anchor Glass has been here nearly 70 years. It operates 24 hours a day, seven days a week. Its disciplinary rules include suspensions of up to three days or dismissal for failing to meet production quotas or breaking rules. A union grievance was pending over the workload in Hammett's department. Employes said pressures had intensified since Anchor changed ownership two years ago and increased its use of efficiency experts.

Hammett earned $9 an hour loading cartons of bottles on wooden pallets. He was described by coworkers as quiet, competent, reclusive and very protective of his wife.

On Saturday, March 16, Judith Hammett went to talk to her husband during a morning work break but was ordered away by foreman Donald Abbott, 48. "She's my wife. She's allowed to talk to me," Hammett told Abbott, according to coworkers. An argument ensued and Abbott called other supervisors, who suspended Hammett and said he faced dismissal. After buying 100 rounds of ammunition, Hammett returned, pistol-whipped a security guard and stalked the supervisors.

He found Abbott and his supervisor, Paul Gabelt, 52, in the quality-control office. Hammett shot them in the forehead, then reloaded. His wife, screaming and struggling with him, tried to stop him. Hammett fired over the heads of coworkers who tried to stop him, but aimed only at his supervisors, witnesses said. He found department manager Ralph Tomaro, 52, and quality-control manager John Coligan, 31, in Tomaro's office and killed both. A fifth supervisor, Richard Hosier, 38, was shot in the chest but survived. With workers shouting at him and diving for cover, Hammett went looking for the plant manager, Russell Watson, but was unable to find him. He returned to the center of the shop floor and shot himself in the chest.

Mayor Goldblum and union president Kaylor said they hope the tragedy will prompt new cooperation between labor and management. Everett would not comment directly, saying, "Our concern is getting things back to normal."