While I agree that "playing the numbers" isn't the very best thing, statistically, almost all active shooters shut down, barricade, and/or take their own lives immediately upon being confronted by an armed threat.

Of course, we can't count on that 100%, but the overwhelming majority of them aren't there for a real fight. Probably because going there to die was in their original plan, unlike the North Hollywood bank robbers. If confronted with an active shooter in the mall, my plan is to use most of my ammo laying fire on the bad guy. That will either take him out of the fight permanently through my action or his, or at least keep him thinking about something else right then. Since I will almost certainly not have a bag full of ammo like an active shooter will, I have no illusions I will run out or low before the first LEO arrive and I will need to retreat. Even if I carried a rifle all the time, which I don't, I doubt I could engage, retreat back to my car, retrieve my rifle and re-engage (this is assuming the shooter was in exactly the same spot they were in when I left, which is unlikely) before the first LEO's are on scene. As an average joe, I wouldn't run back in with no one knowing who I am or why I'm there with a rifle when I see blue lights on scene.

Just my opinion, FWIW.