Two bricks containing threatening messages were thrown through the windows of Christian Liberty Academy in Arlington Heights over the weekend, officials said.
The bricks, tossed Saturday, were apparently in protest of Scott Lively, an anti-gay activist scheduled to make a presentation at a banquet hosted by the Americans for Truth Against Homosexuality, the Chicago Sun-Times reported.
"This is just a sample of what we will do if you don't shut down scott lively and AFTAH F*** scott lively Quit the homophobic s***," said one of the notes attached to the bricks.
The head of AFTAH, Peter LaBarbera, told the Sun-Times he considers the incident a hate crimbe by gay activists.
"If this would have occurred at a gay church, there would have been a public outcry," said LaBarbera.
Police said the school has several window panes and a glass door panel shattered because of the incident.
Arlington Heights police said they're are still investigating the incident.