Calling 911 is a plea to hurry and send over some people with guns. If the school administrators/teachers had access to weapons, they could have either taken out the perp or held him at bay.
Sadly, facts to libs are irrelevant.
We have become stupid, I remember when all glass entrances in any area requiring security had chicken wire type material in the glass. This trained perp could not have made entrance into the school, it would be impossible!