Inexcusable

Whenever a good guy with a gun chooses to take action there is always a chance the police might not know the good guy from the bad when they show up on scene. It's understandable in the heat of the moment. It's not remotely understandable when the good guy's clothing clearly identified him as a security officer.

Black Security Guard Uses Gun to Prevent Violence, Cops Show Up and Kill Him
"Everybody was screaming out, 'Security!' He was a security guard."