I think that puppy is a bit confused and got that way from his "new" home and now you have brought him back and he is confused again...
I know you don't want the dog but try and put him on PETFINDER.com this is so much better that CraigsList....
If I lived closer, I would foster him for you.
Also, check out a rescue group for the puppy....they do wonders with dogs going or gone awry.
Kirsten