I don’t know why you don’t. If shooting happening at a school you’d want the cops there asap. Why? to stop the bad guy. The faster they get there, the faster the badguy can be taking out. But fastest way is if they were there already.
What kind of weaponry would the guard have?
Not sure, Handgun, tazer, pepper spray, the normal sort of cop stuff. I don’t think they would need AR-15s if that is what you mean.