VIRGINIA BEACH, Va. (AP) – Authorities say a Virginia Beach city worker who opened fire on his co-workers in May had spent the hours prior to the massacre sending routine work-related emails and going on ordinary project site visits.

Police said DeWayne Craddock killed 12 people on May 31, hours after submitting his resignation as an engineer in the city’s public utilities department. The 40-year-old Craddock later died in a gun battle with police.

Deputy Police Chief Patrick Gallagher told the City Council on Tuesday night that Craddock cited “personal reasons” for his resignation. He says Craddock then sent multiple work-related emails and drove with two co-workers to conduct routine inspections before returning to the municipal building.

Gallagher says Craddock sent his last email about five minutes before he began shooting.

Investigators are still working to find a motive.