An off-duty Philadelphia police officer fired shots at a man who tried to rob him while the officer was walking his dog in the city's Overbrook section.

Philadelphia police said the incident happened shortly after 11:45 p.m. Wednesday on the 5800 block of Malvern Avenue.

When the assailant brandished a handgun, the officer, who was dressed in civilian clothing, drew his own gun and fired a number of rounds, police said.

The robber then fled south on Hobart Street from Malvern Avenue, escaping apprehension.

Investigators believe the assailant wasn't hit by the gunfire; police said a check of area hospitals yielded no information or suspects.

A few cars in the neighborhood were damaged by bullets.

Police said the department's Internal Affairs unit is investigating the officer's discharge of his weapon.

The officer wasn't injured and nothing was taken from him.

A search for the suspect, described only as a black man wearing dark-colored hooded sweatshirt, remains underway.

The incident happened about a mile away from the location where another man walking his dog was fatally shot during an unrelated attempted robbery last March.

Three teenagers have been arrested in the botched robbery and shooting that led to the death of 51-year-old Jim Stuhlman.

The most recent incident caused some alarm in the neighborhood.

"It startled me," area resident Elizabeth Spivey said of the gunfire. She said she was especially concerned to learn the shooting happened while the officer was walking his dog.

"Being a fellow dog-owner, I'm nervous, walking my dog now at night," Spivey said. She said she planned to adjust her schedule to walk in daylight hours.