Absolutely “no practical difference use to the school kids at all” ... and that's just emphasising the point - it's worse than useless for the guard to immediately get himself killed, because that way he's dead and certainly can't help anyone at all.
So, tell us where everyone was in relation to one-another, what was their distance, who could see whom, how did anyone know the number of shooters etc. etc. etc .... what are you going to do, just charge around the open campus looking for one or more gunmen who are already actively killing anyone who comes near them?
I'll tell you what's “laughable”, in fact what is criminally imbecilic, and that's trying to blame a school guard who was probably in an utterly hopeless position, when the real blame lays with a government and a populace of gun fanatics who insist on owning unlimited amounts of murderous weapons and ammo in their own homes from where any of them can start killing unlimited numbers of people at any moment ... that's what is laughable criminally indefensible in any kind of responsible adult society.