How long is he with you? When they come out the shelter they are very often too active and too exited. A dog need at least 6 months to adapt to his new home. Let the trainer work with him? I think even when it is very precise that the trainer must teach you how to deal with him. Agressive dogs doesnt always need to show agression by a trainer or react very diffrent.Dogs react very diffrent on my approch than when the owner does it. But the importend thing is that the new owbner must learn to deal with it. I am against trainers who take the dog in their own hands. I saw too many dogs react perfect in trainders hands but a mess when back at the owner.The owner needs to learn not the trainer.