Police are searching for a gunman who squeezed off at least eight shots at an officer in Southwest Philadelphia Tuesday night.

The plainclothes officer, who was conducting surveillance in an unmarked Chevrolet as part of an anti-violence effort in the neighborhood, was not injured, police said.

Gunfire erupted about 6:40 p.m. on the 2000 block of South Salford Street, according to Sgt. Eric Gripp, a department spokesperson. The man was wearing a gray hooded sweatshirt and blue jeans. A motive for the shooting was not known.

Officers swarmed the neighborhood and set up a perimeter near 60th Street and Kingsessing Avenue, but a search yielded nothing, Gripp said. No weapon was recovered.

Acting Police Commissioner Christine Coulter said Wednesday morning investigators are not sure the shooter knew he was firing at an officer.

Still, she said, police had identified a possible suspect and he is being sought.