SEYMOUR, Ind. (AP): Investigators still haven’t been able to determine what sparked a workplace murder-suicide last month at a Cummins Inc. facility in southern Indiana.

Police say 37-year-old Qing Chen of Seymour shot and killed his supervisor, 49-year-old Ward Edwards of Columbus, before he turned the gun on himself March 10 at Cummins Seymour Technical Center.

Seymour Police Chief Bill Abbott tells The (Seymour) Tribune that the shooter’s motive could remain a mystery.

Witnesses didn’t hear loud arguments or yelling before the shooting. Chen’s personnel file didn’t indicate issues that could explain what happened, and Edwards’ family wasn’t aware of conflict between the two.

Police believe Chen legally purchased the handgun used in the shooting and the three rifles found in his apartment.

Abbott expects his department’s report on the shooting to be finished soon.

RELATED: Cummins offices in southern Indiana remain closed after murder-suicide