It wasn't the dog's fault. The kid took his bone. The kid may have done it before. The dog shouldn't die because it was the victim of theft.
Good family pets won't maul children that take their bone. When a dog reverts back to its wild and unpredictable roots it should be removed from the family home or from neighborhoods with lots of kids.
Does that mean that it should be put down? Not necessarily. If it could be removed to a more rural area where there are no little children then that could be an option.