Your parents couldn’t have done anything. Those dogs, and yes, I say dog as that’s what they are, probably had dog aggression. It can happen in any breed, not specifically pits. Their owners should have had them better socialized and dealt with the dog aggression if that was the case. I’m really sorry that that happened to your family as I’m sure it was heart breaking. You should go and meet some service dog pitties, that may change your mind on them. But remember, that not all dogs are born good, and not all dogs are born bad. It’s their upbringing, training, and socializing.