TUNKHANNOCK, Pa. >> A supermarket employee brought two guns to work overnight today, blocked the store’s entrances and exits so no one could flee and fatally shot three fellow employees before turning the weapon on himself, Pennsylvania state police said.

State police say it remains unclear why 24-year-old Randy Stair, of Dallas, shot the others and himself in a Weis Market shortly before 1 a.m.

Stair’s shift started when the store closed at 11 p.m. Police said he later took a duffel bag from his car containing two pistol-grip shotguns, brought them into the store and started firing.

At a news conference outside the store in Eaton Township, northwest of Scranton, troopers said Stair spent the first 90 minutes of his shift blocking the entrances and exits with pallets and other items before he started shooting. He fired 59 shots before killing himself, they said.

Stair fatally shot Terry Sterling, 63, of South Montrose; Victoria Brong, 26, of Factoryville; and Brian Hayes, 47, of Springville.

One witness managed to escape the rampage and call 911.

Police stressed that the store was closed to the public when the shooting occurred, and only workers were inside. The store’s posted hours are from 6 a.m. to 11 p.m.

“We are deeply saddened by the events of this morning,” Weis spokesman Dennis Curtin said in a statement. “The safety of our associates, our customers, and the surrounding community is our top priority.”

Investigators were looking at Stair’s online activity for clues to his motive, troopers said.