Hello; I recall that we discussed this sort of thing a few years ago in a dedicated thread and again a few weeks ago in another thread but I cannot recall the thread so I put the link here.
Years ago there was a man who did not show up for work and when investigated he was found killed in his home by two pitt bull dogs he had raised from pups. This current story has some witnesses on the scene is a difference.
Seems the two dogs had been sent to a vets place to be kept locked up after a biting incident and the owner of the two dogs had come to visit to take them out for some exercise (I think in a fenced area). For some reason her own dogs decided to attack her and she died from the injuries.
My take is the dogs had bitten something before was why they were under quarantine. I think if a dog bites some one this can happen so they can be watched for rabies but it may also be for the act of biting alone, that part is not clear. I guess the owner must have figured her own pets would treat her better but was wrong.
These sorts of stories along with the picture where a pitt bull looking dog had chewed a telephone pole in half make me suspicious of that type of dog more than any others. I can not say I have heard of any other type dog turning on it's owner the same way. Might have happened and I just do not know.