I had rescued a chow that was about 9 months old about 8 years ago. We had to put him down, he was cujo. He was such a sweet adolescent but would turn on a dime and bite ANYONE.
I was actually the first one he bit, trying to get him the crate. I brushed it off even though he broke the skin because we had only had him for a week or two. He bit me the second time when I was getting dressed for work one morning. Apparently he had been beat with hangers before because ANYONE who picked up a hanger was attacked! So I took the precautions to make sure he was not in the vicinity when hanging clothes or getting clothes out of closet. Then my neighbor (who had seen at least 50 times over several weeks) was sitting on my couch in the living room watching TV with us and I got up to go help in the kitchen, I heard a shriek and my neighbor was literally in my picture window with the dog biting at him trying to attack him for no reason.
We started at that point talking about it. I consulted with a trainer in my neighborhood that I knew from walking my other dogs. He took the pup for 2 days brought it back and told me flat out the dog will ALWAYS be a bite risk there are so many triggers that we may never uncover them all. So we did what was best for everyone and we had him put to sleep. So sad I loved that little guy and so did my Samoyed...