I would call it in. Things could not get worse for this poor dog, and they could get better. It isn't necessarily you - maybe you had friends over, and one of them called?

I would call Animal Control right now. The dogs needs help. Once he is removed from there, if he really is mentally ill - and who wouldn't be, frankly, he may be put down, but only if necessary, and even that would be a mercy for this poor dog.

By the way, even if the animal is/was vicious, that does NOT excuse this man's behavior. The animal needs care, and attention. To keep it alive in those conditions is heartless and cruel.

I would call animal control. Now.