So yeah, visibly carrying a gun in public is OK. But only if you legally own the gun. A 12 year old can't legally own a gun, so of course your instinctive reaction would be to kill him on sight.
He can legally own a replica of course, but fuck it, shoot him anyway.
Cops shoot a 12 yr old child that pulled a replica gun. The pistol wasn't aimed at anyone before he was shot dead.