"It was not until the bus had travelled away from the victim's location and the role players began to reset for the next bus to come along that anyone realised something was wrong," the sheriff's office said in a news release.
For $15, customers ride the bus, which has paintball guns mounted outside the windows, and shoot at the zombies as the vehicle drives through the maze.
Neither speed nor alcohol was a factor, Sergeant Ward Crawford said.
"The focus of the attraction is the bus creeps forward so the customers have plenty of opportunity to blast away at the zombies," Crawford said.
"This looks like it was just a horrific confluence of events."
-AAP