Police say a U.S. airman who fatally shot one worker and injured another at a Grand Forks Wal-Mart before killing himself did not use a military-issued weapon.

Lt. Derik Zimmel says 21-year-old Marcell Willis personally owned the Smith and Wesson M&P 9mm semi-automatic handgun. Zimmel says Willis legally bought the gun, though the officer didn't provide details on when and where.

The gun was found near Willis at the scene.

Willis was a senior airman stationed at Grand Forks Air Force Base. Police say he walked into the store about 1 a.m. Tuesday and shot and killed 70-year-old overnight cashier Gregory Weiland. Willis then shot and wounded 47-year-old overnight grocery general manager Lisa Braun, who is recovering in a hospital. Willis then killed himself.

His motive isn't known.