Well after all, a wise ghawd has blessed us with munitions and weaponry, so it probably frosts ghawd's balls that we refuse to take full advantage of them!
And by the way, it wasn't just the on-site police officer who hid outside. The three officers sent thereafter also secured themselves behind their cars and waited. When the main body of police eventually arrived, there were four officers cowering in the parking lot and the murderer was at a nearby store enjoying a Coca-Cola.
But never fear, if the Home Ec teacher and the lunch lady had been armed, that shooter wouldn't have stood a chance.