This dog should be gone.
It's not a matter of the dog's breed, in my view. It's a matter of the dog not being adequately controlled by its owner, and more worrisome, having gotten it into its head that biting is acceptable - and possibly even a way to 'rise in the pack'.
Once a dog starts biting complete strangers, that's it. Game over. Period.
Yes, that's harsh. But far too many people are unwilling to control their animals, and one has to ask who is next? How many times do we allow an inadequately controlled animal to injure children, or for that matter anyone else walking down the street? Once? Twice? Ten times?
If you own a pet, you are responsible for the animal - at all times. That includes while your animal is out in the back yard. If it escapes and attacks someone, then you have failed in your responsibilities - both to your pet and to your neighbors.