One usually does not hear about a labrador or a chihuahua killing its owner or a child. This is usually a pit bull, or another not so kind looking dog.
We had two dogs, all of them were from a refuge and were a mix of labrador and squirrel (or whatever was at the party that night). They were more of less intelligent, very friendly (we do not deserve dogs). I wondered how much they would become beasts in worse conditions, compared to z pit bull.