A brick wall on the side of Donald Trump’s campaign office in Denver was vandalized late Thursday or early Friday by a perpetrator or perpetrators who wrote foul language and called the Republican presidential nominee a “thief” and “pervert” in big, block letters. The building’s windows were also defaced.

Sonny Jackson, Denver police spokesman, said a call was made at 7:20 a.m. about anti-Trump graffiti.

“It’s an anti message. We’ll investigate it using all the tools we have at our disposal including viewing (footage from security cameras) to determine who did this,” Jackson said.

Later, at about 9 p.m. Friday, Trump staffers reported a rock tossed through a window of the same headquarters. Television footage from the scene showed a hole slightly bigger than a softball in the window.

Update: A suspect was arrested in connection with the rock thrown through the window.

This isn’t Denver’s first case of political graffiti this election season. Earlier this year, a mural portraying Democrat Bernie Sanders in the city’s Five Points neighborhood was marked with the words “loser,” “sellout” and “traitor” after he endorsed Hillary Clinton.

The Trump campaign had no comment.

Later in the day, at a campaign event in Denver, former President Bill Clinton addressed the vitriol in the presidential race, asking Hillary Clinton supporters to take the high road with Trump supporters.

“What I want you to do is not to treat them the way they have treated Hillary,” Bill Clinton said.

Staff writers Kirk Mitchell and John Frank contributed to this story.