An off-duty Pittsburgh police officer was arrested and suspended from the force yesterday after investigators say he assaulted a man in the head with his service weapon and wounded the individual in the hand as the gun discharged.

Officer Paul Abel, an 8-year veteran assigned to the South Side station, faces aggravated assault and drunken driving charges, Police Chief Nate Harper said at a news conference. The officer has been removed from duty without pay pending an investigation into the incident at 2:11 a.m. at S. 20th and Sidney streets on the South Side that triggered a call to police 911.

Chief Harper said the officer and his wife were patrons at the Town Tavern earlier and had driven away in their car when it was approached at a stop light by two unknown men. The officer apparently rolled down his window and for reasons unknown, one of the men punched him, the chief said.

As Officer Abel's wife ran back to the tavern to summon off-duty officers working there, Officer Abel drove around the block, stopped his vehicle so he could retrieve his gun and then drove back to the scene, investigators said. The two individuals had fled, but Officer Abel parked his car and approached a 20-year-old pedestrian who was uninvolved in the earlier altercation, Chief Harper said.

Witnesses, including responding officers, saw Officer Abel strike the pedestrian in the back of the head with the butt of the gun, Chief Harper said.

The pedestrian's clothing description did not match that of the men who earlier approached the car, and police were investigating why he was singled out.

"The gentleman who was in the physical altercation [with the officer] is an innocent victim as far as we can tell," Chief Harper said. "He was just walking."

The man was taken to UPMCMercy Hospital and was in stable condition. Police would not identify him.

The whereabouts of the two other individuals were not known, nor were other details about that altercation.

Officer Abel was charged with driving under the influence after a breath test indicated he had a blood-alcohol level of .111, Chief Harper said. The legal limit is .08.

Police said an investigator from the office of District Attorney Stephen A. Zappala Jr. went to the scene to oversee the investigation. The district attorney's office approved the filing of charges.

Officer Abel is from a family of policemen. His father, Paul Abel Sr., is a sergeant with the Scott Police Department, and his brother, Matthew, is a fellow member of the Pittsburgh force.

The two brothers were among officers who were involved in the violent arrest of a man at a birthday party in Mount Oliver in 2002.

The man, Charles Dixon, 43, of Altoona, died of positional asphyxia Dec. 23, 2002, two days after several officers had pinned him face down to the floor. Mr. Dixon's family later filed a wrongful death lawsuit, which was settled with Mount Oliver in 2003.

Paul Abel Jr. also had been a top candidate for a position with Scott police, an offer he declined in lieu of a possible promotion within the Pittsburgh Police Bureau.