SAN DIEGO -- A masked thief attacked a security guard with a hammer Wednesday as he and two accomplices attempted to rob an Oak Park variety store, authorities reported.

The three bandits entered Fam Mart in the 1700 block of Euclid Avenue with bandanas over their faces shortly before 12:30 p.m., according to San Diego police.

When a security officer tried to prevent them from going any farther into the business, one of the trio bashed him in the head with a hammer, SDPD Sgt. Diane Wendell said.

The assailant then ran over to a jewelry case and tried to smash the glass countertop, Wendell said. When he was unable to do so, he and his cohorts ran outside and fled in a white Honda.

A short time later, a caller reported seeing three men fleeing into a canyon in the nearby Rolando district. Officers set up a perimeter in the area and began searching, eventually finding and arresting the suspected would-be robbers, according to Wendell.

The extent of the security guard's injuries was not immediately clear.