What do I do now?

JaneyB,
I'm sorry. I know how it is to have setbacks. Believe me. You will get sympathy from me on having a *hard* dog.
 
I'll write more after I take mine for their evening walk (they are SO reminding me right now).
 
Hang in there!

I hope you don't have to euthanize Gandolf. How old is? How many people has he bitten? Gosh, JaneyB, you've been so helpful and honest with me about the importance of managing dogs, and now this has happened.

I don't really have any advice, except to say that I'm so very sorry. Maybe the neighbor is looking for a sincere apology and you can come up with a better game plan after that?
 
How are things now--now that more time has passed? What decisions are being made?

Have you concidered hiring a behaviorlist?  The problem with "managing" an aggressive dog and not working on fixing his problems is that when someone screws up (like you poor DH did) someone else could get seriously hurt, maybe even a child.
 
It is not an easy road but I don't believe you are going to be able to correct his behavior without consulting a behaviorlist - you need someone who can help YOU help your dog.
 
Good luck, be careful with this dog he sounds like he is a real challenge.

We've done gobs of work with this dog - we have worked on training, obedience, agility, consulted with a vet behaviorist, etc., etc.  The behaviorist felt that we could work on some desensitization with him, but that our major mode of action would be to manage his aggression.
 
After much hand-wringing over the past day and a half, we at the moment, have decided to keep him, and hang in there.  We are going to close him off in the yard so he can't even get to the gate regardless of whether it is open or closed.  Additionally, he will be inside at all times when we are not at home.  And lastly, when we pull cars into the yard, all dogs will go inside, so again, the gate issue won't be such a liability. 
 
I think he has come a long way, and is actually a calmer dog than he has been.  And looking for an up-side on the bite incident - the neighbor didn't leave after he was bitten (which I certainly would have done!) - he sat right there on his bike where he had stopped, and maybe Gandolf realized that biting doesn't necessarily get a person to leave/flee. Trying to find a bright side....
 
That said, we are handling what I consider to be a loaded gun, with a twitchy trigger.  We'll have to reevaluate as time goes on.  He is beautiful with us, and has never been aggressive towards us, which certainly helps.  And, he does get along with our other dog, and even tolerates the cat (although at first, I think he would have killed the cat, given an opportunity).

I hit the "Submit the post" button before I meant to!  I also wanted to say thanks for the support - it helps tremendously!

I just wanted to say I know how you feel.  We also have to go thru our pre caution list whenever we do anything.  In fact, just the othe day, I was in the shower, DH ran down to the basement to get something and didn't close our apartment door all the way.  I freaked out because if our neighbor across the hall had come out her door, Willow would of heard here and went right out into the hall!  But, I know how you feel, I have a huge issue with my DH forgetting things and also getting really frustrated that he has to remember them in the first place.

I really don't have help for you,,,but have read your post.
I just want to tell you that I give you so much credit in your thoughts of keeping your dog and how to do it.   I had a dog that I had to watch like a hawk, and she lived for almost 16 years, of course when she got to be an "old lady" she didn't do a lot of the things she always did.  But I do believe if you have a dog that you really have to watch for,,,and know it, you can handle it! And maybe in the meantime...a behaviorist or another trainer might be able to help.
Of course the DH problem I'm not sure what to do with...I have the same thing as I live in a small development of cluster home...anyone that has a dog here besides us,,has a little yappy one and they are always barking and jumping at the door when Bubblegum and I walk by.  At first it was hard to control her when we went for walks because of these dogs..but now she is pretty good. BUT I don't take my dog out to "do her business" without a leash unless its dark and no one is out there because I don't want to take a chance that one of these little dogs are out...Bubblegum can run a whole lot faster than us, if she sees one.  But DH keeps saying "Bubblegum will listen to me!" and takes a chance of taking her out without that leash most of the time.  He is "pretty correct" because most of the time he takes her out before dinner,,,and she has a one tract mind of hurrying  back in to eat. But I don't think we should ever take that chance and he just won't listen.  
Good luck with your dog. Keep up with your plan and maybe in the meantime you can still seek help to correct her behavior.