No fault, no blame, no crime.
If no one is at fault, then no one is to blame, and that’s how most police departments and prosecutors treat these shootings: no fault, no blame, and no crime.
But you can absolutely predict tragic outcomes from irresponsible gun-storage practices, and you can easily assign blame. I’ve never heard of unintentional child shootings in which the shooters were master safecrackers or expert lockpickers, bypassing layers of security in order to find the guns with which they shoot themselves or their siblings. No, they’re just kids, and most kids only ever access their parents’ guns if those parents leave their guns out where they can be accessed.