Well, we don't know how firearms (if any were there at all, hunter could be bow hunter, black powder hunter, trapper) were stored. It sounds as though he had literally no impact on the events, except to have gone to work. The mother seems to have demonstrated particularly poor judgment in that case.
On the other hand, Mr. Carpenter took the state at it's word, that they would be responsible for defending his family. Three of his children were killed while a fourth, who could have stopped the carnage, was denied by the state from having the resources to do so. Maybe she wouldn't have stopped it: Maybe she would have been killed as well. But one thing is certain, a 14 year old girl was outmatched by a grown male with a pitchfork, and because the law mandated that the guns be locked up so a competent person couldn't get to them, three kids died.
And such laws do very little to protect anyone, even absent the massive failures such as this. Very few children are accidentally killed by firearms. Every such death is a tragedy, but if our goal is a completely safe society lets do away with bath tubs, swimming pools and 5 gallon buckets, all of which are responsible for more accidental child deaths than firearms.
