Maybe go knock on their door and see if you can find out any information. If it looks to you like an abuse or a neglect situation, maybe you could ask them if you could have the dog. They might not even care about him and give him to you. Then again, it might not be that easy. I think if its an obvious case, you might be able to call Animal Control. I'm not too sure what the qualifications have to be for them to take a pet though. I had to call them because a girl who lived by me was keeping her cat on her balcony 24/7. The cat always cried and it broke my heart. There was no chicken wire or anything to keep the cat from falling and it was a very small balcony on the third floor. I tried seeing if the humane society could send someone but they couldn't so I had to call animal control. I went to the city shelter though and adopted the cat to take to the humane society. The cat now has a loving home. I hope you can help the dog if he is being mistreated.