An off-duty Chicago police probationary officer has been charged with aggravated assault with a firearm after a confrontation outside a Rosemont bar Sunday morning, Rosemont police said.The off-duty officer, identified by Rosemont police as William Szepi, was a patron of the Park Tavern at 5433 Park Place and was attempting to help bouncers escort people from the bar.Szepi was outside the Park Tavern and got into a verbal confrontation with people and pulled a 9 mm Glock 19 semiautomatic pistol and pointed it in front of him, Rosemont police said. Another patron saw the gun and disarmed Szepi.Security was called to the Park Tavern and Szepi's gun was recovered by security and handed to Rosemont police, who responded to the bar at about 2:54 a.m. after a report of a fight.Szepi was taken into custody and charged with aggravated assault with a firearm, police said. Szepi has been released on bond.Rosemont police contacted the Chicago Police Department Bureau of Internal Affairs. CPD Internal Affairs said the officer has been suspended pending the outcome of the investigation and court process.