Being a MASS shooting, by definition it wasn’t stopped before or during its happening. The conclusion is that lack of an easily accessible gun to stop the perpetrator RESULTED in the MASS shooting. Ultimately, the presence of a “friendly” gun DID prevent additional killings — even of the gunman.
I read a study recently that said when the cops arrived and stopped the shooter, average 18.? people killed.
BUT when a person (citizen or any kind of profession) with a gun was there, the average was 2.3 killed. So that wouldn’t qualify as a mass shooting.