Fact: Of the 2,500,000 times (per year) citizens use guns to defend themselves, 92% merely brandish their gun or fire a warning shot to scare off their attackers.
Source: http://www.gunfacts.info/pdfs/gun-facts/7.1/Gun-Facts-7.1-screen.pdf
I would contend that there would be no "active firefight" at least 90% of the time that a teacher uses a gun to stop a shooter.
90% is a lot.
In my DARK days as a yoot, I used to rip off vending machines in NJ.
I had a bunch of keys and not many open most machines.
and YES, if i knew one of the attendants had a gun, and if i DIDNT know NJ’s gun laws, I would have gone elsewhere.
Feel bad for what i did and asked forgiveness and repented as well as I could.
But YES, a guy with a gun is not the one to rob