CHICAGO (AP) — An off-duty Chicago police officer was shot when he was attacked while stopped in his personal vehicle at a traffic light on the city’s South Side.

The officer underwent surgery shortly after the Monday incident and is reported in fair condition. Police Superintendent David Brown says the officer was alert when he was transported by officers responding to the shooting scene to a hospital.

Brown said the circumstances of the shooting were unclear, saying there was talk of a carjacking attempt, but that hasn’t been confirmed.

On Sunday, a Chicago police sergeant received a graze wound to the chin while standing in the parking lot of a police district. He was treated at a hospital and released.