Well since you always have an idiot sneak into the event sooner or later (hard to catch everyone right off the bat when you have 200+ people in the event) the CMs have found relatively simple way to deal with it. Not fool proof but should helpd weed out the jerks like this.
I believe they will turn kill shooter on for a the first 15 minutes or so. That way if a jerk slips through the cracks all he will do will end up is shooting his own but down. Plus with the chaos of trying to make sure everything is going well, everyone is suited up, and all the other stuff a setup CM has to do with 200 people it gives him a window to get everyone up and then check again or here from you guys about some noob being a jerk.