Sad! But you did the right thing by returning him where you got him. He'll find a home where someone can really work with him without risking children and other pets. Good luck finding another dog! I've been reading that with the economy as it is, animal shelters are overloaded righ tnow with pets whose owners just couldn't afford to take care of them anymore. It's sad, but it also means there are a lot of good animals out there that could be the perfect fit for you.
Poor Tuffy! I'm sad that you had to return him but you did the right thing. I had that same thing happen to me with a french bulldog adoption and had to return him after 2 weeks of trying to correct his behavior. It was hard to return him even though he definitely wasn't the right fit for our family.