A Chicago police officer has been benched after opening fire during a drunken gunfight early Saturday in Austin that left a companion seriously wounded. He initially failed to disclose his involvement in the incident to investigators, according to oversight officials and sources. The incident unfolded about 1:25 a.m. Saturday when a Jeep Grand Cherokee carrying two off-duty police officers, a woman, her boyfriend and his brother stopped in the 1000 block of South Mayfield Avenue, according to internal COPA documents obtained by the Sun-Times. The woman's boyfriend, who was driving the vehicle, is best friends with one of the off-duty officers. The group had just left a birthday party at Legends in Maywood. They were dropping off the brother, who lives on Mayfield, documents state. As the 26-year-old exited the vehicle a silver-colored Chevy Malibu pulled up in the intersection behind the Jeep. As the man walked toward his residence a person wearing all black clothing standing near the trunk of the Malibu fired shots in his direction, documents state. The man was struck in the forearm as he ran from gunfire. The woman in the Jeep opened the front passenger door, leaned out of the vehicle and fired several times toward the intersection. The 26-year-old got back into the Jeep and was taken to West Suburban Medical Center in Oak Park, where he was listed in serious condition. During their preliminary investigation high-ranking CPD officers observed that the two off-duty cops appeared to be intoxicated, according to the documents. The Bureau of Internal Affairs responded and administered Breathalyzer tests. While speaking with detectives the woman told investigators that one of the officers had asked for her gun during the incident and that she had handed it to him, according to COPA. The officer failed to mention this detail to officers who spoke with him. He also either denied he discharged a firearm, or didn't mention that he had. Several fired casings were found in the back area of the Jeep. When confronted with that information the officer acknowledged that he "possibly" discharged the firearm, COPA states. The officer said that when the woman handed him the gun he performed a maneuver as if to clear an ammunition jam and "it possibly discharged."Police officials later informed COPA that one of the off-duty officers had opened fire, the oversight agency said. The officer, who was hired in 2017, has been relieved of his policing powers, according to a department spokesperson. The other officer is active and assigned to the 7th District. The shooting was partially captured by third-party cameras, COPA said. No one has been arrested. Officers from Oak Park responded about 1:40 a.m. to a call of a person shot at the hospital and watched a vehicle "flee the scene," according to Oak Park police. A vehicle matching its description was spotted a short time later and was ultimately stopped near Austin Boulevard and Madison Street, where officers saw it was riddled with "multiple bullet holes."The driver was then asked to step out of the vehicle, and officers found a gun in his pocket and another under a seat. He had a valid license to carry the weapons publicly, Oak Park police said.Chicago police officers showed up "and took over the investigation" because the shooting happened in the city, Oak Park police said.