Ok, so the mom and grandmother knew this dog was a danger but they made the decision to go for a walk by his house? Not only that but they brought along the baby stroller that was probably squeaking or making a noise that would agitate the dog. Sorry, but they are as much to blame, if not more because they are adult human beings, for what happened.
They forgot to bring a firearm or a hunting knife with them on their walks. They decided to be a victim instead of refusing to be one.
Those squeaky strollers can be a killer!