Police were called to Famous Footwear at 1621 E. Monte Vista Ave. at about 5:20 p.m.
The store manager told police she confronted a man in the store who was trying to steal shoes. The man got angry and left.
While the manager was on the phone with police, the man came back and sprayed her and an assistant manager with Mace, grabbed some merchandise and fled in a silver Toyota Camry with tinted windows, police said.
Police searched the area but did not find the man.
He was described as a black man about 5 feet 7 inches tall with a thin build. He was wearing a grill in his teeth, a black leather jacket and a New York baseball cap.
Anyone with information about the crime is asked to contact the Vacaville Police Department at (707) 449-5200.