The best video was posted by Derek years ago. Owner of a jewelry store is shot to death trying to chamber a round.
Maybe someone can find it.
I think 5 years old is plenty old enough to teach kids about safety. Shooting really depends on the individual kid. My son started shooting with a single shot pellet gun at 5. He used to stand on a milk crate and rest the rifle on the deck railing. He also started to recite the safety rules. He got his first 22 rifle at 6. One daughter did not shoot until she was 11 and my youngest is 15 now and has no interest in shooting.
But all of them learned about firearms safety as soon as they were old enough to understand "NO". As in " NO! Don't put your hand on a hot stove!" or "No, Don't put a fork in an electrical outlet!"
I think they teach kids "stop, drop and roll" and "stranger danger" in pre-school and kindergarten.
Carry gun, nightstand gun, shit hits the fan rifle, all have one in the pipe and spare magazines handy. All are secure and kids taught not to play with guns. More worried about other peoples guns than mine. Guys that take firearms seriously are not the issue. It's the guy that doesn't, that keeps a gun in a shoebox in his bedroom closet that you have to worry about. He thinks his kid will never find it. He is wrong.