The Virginia Beach gunman appeared to target supervisors in his department in the early moments of a shooting spree that left 12 people dead on Friday, according to a survivor of the attack and a city councilman.

Authorities in Virginia Beach say they are still working to determine what motivated DeWayne Craddock to bring two handguns into his municipal office last week and begin shooting.

In the meantime, the survivor and the councilman described how Craddock walked down a hallway past a number of employees on the second floor of Building 2 before firing his first shots inside of the building, in an area where senior engineers and supervisors sat.

“He was looking for specific people apparently, at least at first,” said Louis Jones, a Virginia Beach councilman and former mayor whose grandson, Jack Jones, was interning in the public works department and working on the second floor when the shooting occurred.

Craddock, a longtime engineer in the city’s Department of Public Utilities, submitted a short letter of resignation the morning of the shooting. He wrote that he was giving his two weeks’ notice “due to personal reasons,” and that “it has been a pleasure to serve the City,” according to a copy of the email released by the city on Monday.