RANCHO BERNARDO, Calif. -- A tall muscular man in his 30s robbed a Vons grocery store in Rancho Bernardo at gunpoint, San Diego police said.

The robbery at the Vons grocery store at 11986 Bernardo Plaza Drive occurred around 8:50 p.m. Wednesday, according to San Diego police Sgt. Alan Hayward.

The gunman pretended to be interested in buying a few items, then pulled out his weapon and demanded money when the clerk opened her cash register, Hayward said.

He then demanded a manager open another cash register and told her to give him more money, Hayward said.

Both the clerk and manager complied, and the robber fled on foot with an undetermined amount of cash, according to Hayward.

Police described the robber as a black male in his 30s, 6 feet 3 inches, last seen wearing a blue polo shirt.