The behavior of an armed citizen will be CLEARLY different from a maniacal sociopath walking around a school, church, mall, office, or wherever spraying bullets. Seeking cover, calling 9-1-1, maintaining quiet alertness, and not shooting at others would be clear indicators of who is a "good guy" and who is a "bad guy" in that kind of scenario.
> The behavior of an armed citizen will be CLEARLY different from a maniacal sociopath walking around a school, church, mall, office, or wherever spraying bullets.
You hope. But how do you know?