SAN YSIDRO, Calif. -- A man waited in a storage room of a San Ysidro shoe store until the business closed and then robbed a clerk of an undetermined amount of cash, a San Diego police sergeant said.

The robber was wearing a ski mask and dark clothing when he approached the clerk of the store at 4211 Camino de la Plaza shortly after 9 p.m. Saturday, Sgt. Alan Hayward said.

He displayed a chrome semiautomatic handgun and ordered the clerk to open the cash register, grabbed the money and ran out a back door, Hayward said.