If there are guns to be easily found.
Make it harder to find guns, and bad guys can't get them easily. Where it is easier to procure guns, gun violence is increased. Where it is harder to get guns, fewer people are killed. Gun dealers don't want that message getting out though.
I don't think the US has ore bad people than anywhere else. People are people. Bullies who can't get guns readily are easier to stop.
The correct anecdote would be
"Guns don't kill people (all by themselves), people (find it easier) to kill people (using guns)."
John