A majority of perps described as "determined shooters". A majority of shooters had close personal association with at least one of their victims. Now the fun part: 30% of shootings occurred in emergency departments... and fully 50% of those emergency dept. shootings were perpetrated with weapons that the perp did not possess at the time he/she entered the hospital. In other words, the perp managed to take a gun off whatever security person or cop was around at the time.
Think about that when you consider arming teachers, school administrators, etc. In six sigma management consulting, the objective is to remove opportunities for error. If 15% of hospital shootings occur simply because of the occasional presence of security firearms in the ER, what's gonna happen when the schools get flooded with firearms in the hands of distracted educators??
And if you want to know what law enforcement thinks about the concept of removing the opportunity for error by removing firearms, visit any prison. The guards that work among the inmate population DO NOT CARRY GUNS. Take a guess as to why.
Now re-imagine arming the teachers. Still a great idea??