(AP) – Missouri State University officials are trying to decide how, or if, to monitor fake guns used on campus during a popular Zombie game.

The “Humans vs. Zombies” game drew 500 students during a week in October. Participants try to tag other people, who then become zombies. The humans can defend themselves against the zombies by stunning them with Nerf guns or a balled-up sock.

During October’s game, a professor called 911 and put a classroom on lockdown after thinking he saw a gun. And the university’s safety and transportation department got several calls on its non-emergency number while the game was being played.

Department director Don Clark says banning the Nerf guns is a possibility but he is not sure that’s the right solution.