Been there done this.I'm sorry that you have to deal with this, and I hope that whatever you decide to do works out well for you. As Ridgerunner pointed out above, though, be careful that the local ordinances are on your side before you call the cops.
It's not the chicken keeping to focus on.
It's the dog being set on another animal.
That, everywhere in the US, is animal cruelty. Had something similar happen about 10 years ago. Cop told me flat out, deliberately setting a dog on an animal or pet belonging to another person is against the law.
Neighbor who owned the dog got a very angry cop knocking on his door and was read the riot act. He immediately secured the dog and got it out of the neighborhood shortly after. I didn't choose to press charges, but the cop made it clear that with animal cruelty charges, I didn't have to. The law would.