Who Stops a "Bad Guy With a Gun"?

I took an active shooter training class at our sheriff's dept some years ago. At the end they had a Q&A period, and nearly all the questions were coming from obvious gun owners who just wanted one of the deputies there to give them the ok to shoot during an active shooter event, just some sort of official recognition that they were in the clear to do it. The deputies weren't having any of it and the farthest they would go was, "You do whatever you feel is necessary to stay safe and protect yourself." I'm assuming they couldn't endorse vigilantism or for citizens to be bringing guns into active shooter situations, since even the firearm accuracy of cops is supposedly only ~30%. The people in the crowd kept coming up with ever more wild scenarios, just trying to get somebody to tell them it was ok. "You're telling me, that if there was an active shooter that had your wife and kids hostage, and I'm standing there with a gun, you wouldn't tell me it was ok to take the shot?" was one question I remember a guy asking. It was like, they're obviously not going to tell you what you want to hear, can we move the fuck on?