Red "X" mard on my apartment door and car windshield?

Last Friday we asked the management to do a pest control in our apartment and they scheduled it on next Wednesday. But yesterday(Sunday) we saw a RED pastel "X" mark on out apartment door. we though the management has put it in for the pest control but we were really surprised to see a small X mark on our car windshield also. We got scared. Do you have any idea why in the world someone will put some sign like this in the apartment door. We are a bit scared!!!!!