There's a lot to consider if you want to try and be a hero. If all of your bullets don't hit the mark you're legally responsible for every one. What if police or another armed citizen shoot you? What if you accidentally shoot another armed citizen? What if your presence slows police response leading to more people getting killed. (Yes they are going to stop to disarm, frisk and hog tie you before moving on) I've been talking to a lot of LEO and MIL about this very subject lately. I'm putting together a program we will offer for free at my gun club called "Active Shooter for the Armed Citizen. East Ellijay Police Chief told me the other day "if my guys get a call about an active shooter at the Walmart and when they show up your the first guy with a gun they see you're getting shot".
I'd also like to point out that sadly the vast majority of gun owners don't even have near the skill set or mind set necessary to act successfully in such a situation? But I'll also concede that anyone can get lucky on any given day and the best trained person can get unlucky on any given day.
you're exactly right, that the majority of gun owners -- and those who concealed carry -- don't have the first clue how to tactically deploy their weapon in a safe an effective manner. AND that sadly applies to many LEOs as well. I've got family who do annual training for LEOs in a metro department and the stories of their stupidity with firearms make for regularly holiday laughs. Lots of these guys do their annual qualifying and don't put a round through the gun otherwise.
I've had training (not enough by my standard, but is there such thing as enough?), and i regularly have the conversation wiht a close friend who is a LEO about this topic -- specifically as it pertains to our church. We, and several others, carry at church. We regularly discuss that there is not a safe way to engage a threat/active shooter based on the lay out of our building -- background risks, over penetration, etc.
In my 20s when i had just gotten my GWL I thought i was gonna be wyatt earp if some bad guy went all LA Bank Robbery any where near me. Now i know 2 things should I encounter an Active Shooter 1) the safety of my family is top priority, and 2) If i can get away with out deploying a weapon I will seek to do so. If i ever have to get to an option #3 (deploying weapon), I pray for judicious marksmanship, and LEO first responders with great judgment and discretion --- but when i hear "police" yelled, you can rest assured I'll be spread eagle, face down on the ground with my gun tossed aside.