You say that the kids life is more important than the cats?
If a four year old eats a pet, then obviously that four year old does not fit in society. To me, I rather live in a world with one less "pet eating four year old" than live in a world with one less family pet.
I have no remorse for the kid, at age four, you know what is right and wrong, only a sick minded kid would even think of killing. I know when I was four, I was smiling, laughing, walking, and dressing up as a fireman. But I was definately not killing my pet cat. That is just sick, and deserves some kind of action.