SOUTH BEND, IND. ? A man shot four co-workers to death at an aircraft parts plant Friday, then fired at police from a stolen company van during a high-speed chase that ended with him killing himself.

The van was still moving when the gunman shot himself while approaching a roadblock across the Indiana state line near Niles, Mich., said Capt. Richard Dragomer of the Michigan State Police. The van ran over some mail boxes and stopped when it hit a tree.

The gunman was identified by police as William Lockey, 54. Police said they weren’t sure of a motive, though one co-worker said the man was worried about losing his job.

Two other employees were wounded in the shooting, and three officers were hurt by flying debris or shotgun pellets as they exchanged gunfire with Lockey during the chase. Police said Lockey stopped occasionally to fire at police and reload before driving off again.

“It was a gunbattle all the way out of South Bend,” Dragomer said. “He was shooting all the way.”

Police said the shooting began about 8:15 a.m. at Bertrand Products, a manufacturer with about 50 employees.

Employee Sharon Zalas said the gunman brought a grocery bag at the start of his 7 a.m. shift.

“Everybody went to work, the next thing we heard was pop, pop,” Zalas said. “We thought maybe it was one of the machines because we saw one of the guys running. Then we saw the gun, and he was shooting and shooting and shooting.”

Zalas said she believed the gunman, who worked in the shipping and receiving department, was targeting particular co-workers.

“Because he used to get in little squabbles with them because he didn’t get his merchandise in time to ship it out,” Zalas said. “He was sort of rigid, kind of a lone wolf. He was afraid of losing his job.”

The dead were identified as Craig Schafer, 50; John Contadeluci, 47; Dave Arpasi, 73; and Robert Downs Jr., 42.

A Michigan officer was treated for a cut from a gunshot-shattered windshield, and two Indiana officers were also injured during the chase.

One of the wounded employees was hospitalized in serious condition; the other was listed as stable.

It was the second factory shooting in northern Indiana in the past four months. On Dec. 6, Robert Wissman fatally shot the manager at Nu-Wood Decorative Millwork in Goshen, about 25 miles east of South Bend, and wounded six others before killing himself.