Anti-Trump protesters stomped on the American flag outside of Fox News’s townhall with GOP frontrunner Donald Trump on Sunday.

Fox News reports the atmosphere outside the town hall event location at the University of Wisconsin-Milwaukee’s Mainstage Theatre was tense and aggressive.

An anti-Trump protester was captured stomping on an American flag and then confronted U.S. military members and bystanders.

Police calmed the scene.

“Tactics like that definitely do get people upset in this country, and people of all political stripes, not just Republicans,” Fox News’ John Roberts reported.