“The armed volunteers did not fear any threat of being shot by onlookers, who mistook them for being real shooters, due to the fact that the school is a gun-free zone and everyone in the room was unarmed. “
Never, ever, bet your life that anyone whom you haven’t just frisked is unarmed.
Even if nobody there was armed, they were lucky someone didn’t tackle one of them and beat the crap out of them. It would take quite a while for “it’s a drill” to sink in to the person doing the beating.