My neighbor is Bi-polar and he has threatend my dogs life and yells at my wife when im at work. Does that give us a legal right to break our lease?

We live in a duplex and the connecting neighbor is Bi polar and he has threatend my dogs life. he has yelled at my mother in law and my wife. We are very concerned that he will one day lose it and actually harm our dog and worse, my family. He is a very angry man and his temperment is terrible. We hear him arguing with his friends and his parents in a very angry manner often. Recently my dog had swollen cheeks and his eye swollen shut and i called the vet and they suggested i just give him benadryl, but I had a concern that our neighbor was tossing poison or something for our dog, into our yard. Just today we found a hamburger in our yard that our dog was eating and we are thinking that it has been poisoned. What kind of legal options do we have to either leave our lease without penalty or pursuit a civil charge against him.