The dog is at the vet.'s even as I write this and when this perculiar -- and dangerous behavior -- became apparent, we have kept my son the dog in question apart. I should hate to find another home for this dog, but I know that this is a very real possibility. I wonder if anyone might have any ideas about what might have triggered this behavior? Until this happened, this dog was "o.k" with my son -- not overly thrilled, but accepting of the addition to the pack. As I stated, this behavior is sudden.