Thing is that it's ridiculously easy to shoot up a bunch of unarmed people before law enforcement arrives, so AI could do this easily. Maybe human controlled assailant after the SWAT arrives. Human controlled students could then use tactics to take out the distracted assailant.
Perhaps some good could come out of it with better counter measure tactics, though it could potentially lead to better assailant tactics as well. It also risks glorifying assailants even though the goal is to neutralize them, possibly encouraging even more real life mass shootings than what we already have.