Police are probing an incident in which an off-duty Montgomery County police officer drew his weapon during a confrontation with someone who had thrown a water bottle at his car in a University of Maryland parking lot Saturday afternoon, authorities said.

The incident occurred just around the time Maryland's football game had started in a parking lot adjacent to Ludwig Field, where tailgaters typically hang out, said University of Maryland Police Chief David Mitchell.

Mitchell said the officer told investigators he was driving through the lot when someone threw a water bottle at his personal car. The officer told investigators he got out and confronted the people he believed had thrown the water bottle, and that led to some “pushing and shoving,” Mitchell said. He said the officer drew his gun and held two people at bay until University of Maryland police arrived, called specifically to assist the off-duty officer.

Mitchell said the person who threw the water bottle told investigators he did so because the officer had bumped his hand with his side view mirror as he drove through the parking lot. He said University police had assigned a detective to the case and would present their findings to the Prince George's County State's Attorney's office. They also notified Montgomery County officials of what happened, Mitchell said.

Mitchell said investigators determined the officer had not been drinking before the confrontation. He said police would not immediately identify those involved because no charges had been filed in the case.

Montgomery County Police Capt. Paul Starks, a department spokesman, said University of Maryland police are handling the inquiry. “Members of our department have been in contact with them and will continue to do so,” Starks said.