Tinley Park canceled the final day of its Armed Forces Weekend Carnival on Sunday after police said a “flash mob” of 400 teenagers showed up at the weekend festival on Saturday and started fights.

Police said that “another flash mob” was being promoted on social media for Sunday and the event was canceled over “safety concerns.”

On Saturday, a group of teens began running through the parking lot of the 80th Avenue train station, where the carnival was being held, and began “fighting with each other in an attempt to cause chaos and disrupt the event,” police said.

At one point there were reports of shots fired at the station but the town posted a Facebook message telling the public that “there has not been a shooting as rumors are spreading! The police are trying to maintain order and evacuate everyone safely ... there have been fights and there is a lot of confusion.”

A police officer was injured trying to break up a fight and was treated at South Suburban Hospital Saturday evening, police said. Five teens were issued citations for fighting in public.

Most of the teens taken into custody were released to their parents, police said.