This is some absolute bullshit “good guy with a gun” mentality.
Has any shooting to your knowledge been stopped by anything other than a self defender, a cop, or the guy shooting himself to avoid said cops? The common denominator in any of those is “a gun held by someone intending to stop the shooter.” (In the case of the shooter shooting himself, it is generally still to avoid a group of guys with guns intending to stop the shooter, the cops.)
You’re one of those “harvard says the good guy with a gun is a myth” guys, aren’t you? I can smell it in your comment. Seems you missed an important note from that study however: While defensive gun use is “more accurately estimated at 100,000 DGU/yr,” instead of the CDC’s reported estimates by Kleck and Lott, all gun deaths including suicide and accidents are still around 60,000 a year, adjusting for intentional homicide only gets 12,000/yr, and just for fun those scary black rifles that are “the problem” are only used in ~500 deaths/yr. Furthermore their study discounted entirely what is likely the most common form of defensive gun use, defensive display, in which the sight of the firearm is enough to scare off the attacker. This means that Harvards 100,000 estimate would be low if we included them. Still though, even with them pretending defensive display is all lies, 100,000>60,000>12,000>500, meaning guns are used far more for defense than murder or suicide.
What can we take away from this? Well, if 100,000 is SO infrequent that we can categorize it as a “myth,” what then is 60,000 or 12,000 or 500? If 100,000 dgu is a myth, so to must be our 60,000 gun deaths at 40,000 less.