I'm sorry guys, I believe the op did what was best for her family--and yeah, I've been involved in rescue for years too. In the beginning I had that attitude of "I'm gonna save them all" but you know, I was about 7 yrs in when I realized were spending funds we didn't have and copious time we didn't have to save one aggresively inclined dog because we would make him a cause--after all, it's not his fault, they all deserve a chance, yadda yadda yadda. I was especially bad for this--afterall, I'm the dog trainer who specializes in aggresive dogs! At about 7 yrs in I stopped to look at things and realized we were killing perfectly friendly, lovely nice dogs--why?? cause there was no challenge in them, there was nothing "special" that made us go to bat for these dogs--everyone just figured that the nice dogs would do ok without any extra help--but they don't--they end up dying while we pour our lives and money into a dog that really should not be adopted out and when it does get adopted out it's going to have 15 precautions attached to it. There are only so many homes out there--it's unfortunate but it's just that simple, why are we killing the nice dogs just so we can pat ourselves on the back and say we saved the unsaveable??? It doesn't make sense to me anymore.
In this area there is an organization who has become known for adopting out these types of dogs-so much so that I really want nothing to do with them. They adopted out a large lab cross who had "only ever growled and shown teeth" the new owners were told it was just because the other people had not excercised it enough, they were told the dog hated having his collar grabbed--etc, etc, etc, etc. The dog mauled and damn near killed the dog walker his new and really nice owners had hired--these people had a 2 yr old!!! Frankly, I testified in court against this rescue organization--normally I would never support attacking a rescue organization, but in one year, I had seen 11 dogs from this very organization that should never have been adopted out--their new owners were paying me through the nose to attempt to save the dog because it was just plain snarky--all 11 of those people would have saved a nice friendly dog, so you can pretty much count on the fact that 11 nice dogs were killed so these nasty dogs could have a home and this particular rescue organization could continue to say "we're no kill--no matter what"
So I'm sorry, but I've learned over the years that they just can't all be saved and in my humble opinion, our efforts at saving are best made in the area of saving the dogs that don't have temperment problems.
Milky way, I've got to be honest, I don't agree with you that this dog could be fixed and I think you'd be hard pressed to find proof that behavior modification would actually solve this problem. The owner would NEVER, EVER be able to trust this dog--I don't know about you, but I have pets to enrich my life and make my life better and I don't think living constantly on edge and having to be hyper vigilant because I KNOW my dog is a fear biter and just about anything could set it off. If this was a one time issue, I'd wholeheartedly agree that they OP should try some behavior modification and some obedience training, but this was not the first time--how many near misses should one endure before they take action. As a trainer I can tell you that all the training in the world would not make this dog trustworthy--and frankly, as a trainer that's exactly what I'd have told this owner in an initial consult. Should she have been watching the dog closer-sure, but no human, no matter how diligent is going to be 100% on top of it 100% of the time and unfortunately it only takes a couple seconds for tradgedy to occur. With a dog of more stable nature a warning would be issued first and therefore those couple seconds of inattention would involve a warning by the dog instead of a nasty bite.
I'll be honest, the reason I seldom advice families to adopt from a shelter is because of exactly the statements made here--that in your rescue this dog could then be placed with another family frightens me. In interviewing people there is no real way to know for sure how much experience and knowledge they have. Recently we sold a dog to someone who swore up and down he wanted a working shepherd, he was going to do schutzhund, he was gonna start tracking ASAP, he came to us because he didn't want one of those "unstable, wobbly show shepherds" We got the dog back after a month--he didn't have a clue what was involved with puppyhood in a working dog. He was shocked that this pup had no fear--but he knew enough to fool us--and we're not newbies.
Also Milky Way, I've said this before, but you say nobody PM's you--the reason for that I'm imagining is that you come out with guns blazing and a my way or the highway attitude. Try a gentle approach and be a bit more understanding of the trauma this poor mama must have felt when she saw her babes head in the dogs mouth.
It's all unfortunate, but there's really no happy ending to be had here. Unfortunately, if the OP had kept this dog and in the future it had badly hurt her son--she is the only one who would have to live with it for the rest of her life--not you, not me and not anyone else--just her.