A "good guy with a gun," an armed security guard at a Chicago area bar, stopped a shooter. When police arrived on the scene, they shot and killed the security guard. I don't know that "armed security guard at every bar, school, mall, movie theater, church, synagogue, and literally every public place" is the way to go
https://wgntv.com/2018/11/11/multiple-wounded-in-robbins-bar-shooting-police-say/