Once dogs are in the midst of an attack, they can be oblivious to interference by the owner and even attack them. I don't buy the theory that dogs just suddenly go crazy one day. The fact that you have raised pups from an early age doesn't mean that you can control them or that you have taught them to be obedient or that the dog or dogs actually have any regard for you. There are plenty of dog owners who control their dogs through cruelty and fear and that kind of owner is likely to be guzzled by a dog in the throes of blood lust.
Our Shibas, being Shibas, had a high prey drive but you could stop them from killing an animal by inserting your hand in their mouth because they would never, ever, bite us, no matter how carried away they were with the hunt and Shibas can become deaf to commands when they are hunting. In fact, even our German Shepherd who wished death on all cats could be made to leave them alone and never, ever bit one of us or any other person who was allowed in the household. She and our other dog, a terrier/$#@!er spaniel did chew up a housebreaker once as evidenced by the blood smears on the walls up the stairs and at the door where he escaped. He never got a chance to steal anything.
The point is, if your dogs are truly well disciplined and properly socialized, they don't just go nuts. Big dogs require more care and attention to their breed characteristics and common sense perception of their personalities because they are capable of hurting people and animals. The world is full of incompetent and irresponsible dog owners who will say anything to avoid personal responsibility.