PHILADELPHIA (AP) — Two Philadelphia police officers working at the city’s Fourth of July celebration suffered graze wounds when shots rang out late Monday night, causing scores of frightened people to flee the scene on foot.

It’s not clear what sparked the shooting, which occurred around 9:45 p.m. ET Monday in front of the Philadelphia Art Museum, or if either officer was the intended target. One officer suffered a wound to the forehead — with officials saying the bullet was found in the officer’s hat — while the other was wounded in the shoulder.

Both officers were treated at a hospital and were later released. No other injuries were reported in the incident and no arrests have been made. Investigators have not yet determined where the shots were fired from or how many were fired.

Speaking with reporters Monday night after the shooting, Philadelphia Mayor Jim Kenney said the increasing violence in the city has left him “looking forward to not being mayor.” He also cited frustration over efforts to toughen gun laws.

“This is a gun country. It’s crazy. We are the most armed country in world history and we are one of the least safe,” Kenney said. “I’m waiting for something bad to happen all the time. I’ll be happy when I’m not mayor and I can enjoy some stuff.”