One of the NRA spokes idiots was shot by her own ~4 year old that she'd been proudly and publicaly training to use guns to prove how safe they were around kids if you only trained them how to treat them.
IIRC she left her "I need a gun for personal protection at a moment's notice" gun in her handbag that she threw on the back seat of her car (outside of easy reach in an emergency...) next to her toddler who then pulled it out and shot her in the back through her seat.
There are also so many pictures of American "guns rights" people with everyone in the family from the pre-schoolers up to the paralyzed, blind granny with their guns.
I suspect in this case it'll turn out that (like in so many other instances) the parents had the gun completely unsecured in the house where the kids could get it, IIRC gun deaths are now the leading causing of childhood deaths that aren't illness related in the US, with far more of them than car accident related deaths which used to the the main one and it'd depressingly common for a very young child to get hold of daddy's gun and shoot mommy, sis, brother, or their friend.