I would be interested in what people who have first-hand experience in mass shootings think about the idea that a good guy with a gun can usually stop a bad guy with a gun. Are there any surveys about that?
The closest thing I've found is a survey of incarcerated felons done by Crime Prevention Research Center, and most of the incarcerated felons think that abolishing gun control would lead to fewer mass shootings. However, I'd guess most of incarcerated felons don't have any actual experience with mass shootings.