The robbery happened at 9:30 a.m. Monday in the 2200 block of North State Line.
The suspect was armed with a handgun and demanded money. He left the building on foot. No one was injured.
He is described as wearing dark covered clothing, possibly all black, with a ski mask, gloves, and a hoodie. Employees believe he was in his 30s, about 5 feet 9 inches tall and a medium build.
Anyone with information is asked to call 911 or the TAPD.