I really hate it when people from other nations cherry pick certian isolated insidents and claim that its a national issue or problem.
Anyone that allows a fire arm to fall in to the hands of a minor and said minor shoots anyone the owner of the gun should face prison.
I dont care if its a sister shooting a brother, you shoot your kid "accidently" or your kid shoots himself.
You own the weapon, you are the parent. Act like it.
Do you leave your car running with your 5 year old inside bouncing around?
Do you let your child play with matches?
And futhermore, anyones stupidity or criminal activity does not trump our 2A rights.