I'll say what everyone else is dancing around: The dog should be put down. It is a danger to other animals- and likely humans, too.
I don't interpret these responses as "dancing around" anything. SIL has trained dogs such as this with great results. An animal behaviorist is definitely in order, as is a full medical exam if there hasn't been one. If the dog is not neutered (my apologies if that's stated somewhere and I missed it) that would be step number one. One of the major causes of inappropriate dog behavior is inappropriate owner behavior, i.e. your tensing up is causing the dog to snap. While agree the breed doesn't lend itself to necessarily being a social dog, there are many breeds that some would like to eliminate for the same reasons. Before you take the potentially unnecessary step of euthanizing the dog, PLEASE try a behavior specialist who can analyze the dog AND you. Also, please keep us informed as to how you make out.
