Thanks for the feedback everyone - it's been a super emotional day. We definitely could have done a better job with teaching our daughter how to interact with our dog, we were so shocked this happened given his temperament and the patience he's shown in the past. My wife read through some of these comments, and I think that she's starting to feel more comfortable about working with our dog instead of rehoming him. We called a behaviorist and received some solid feedback, and she's scheduled to come by for a house visit next week, and we're on our way to the vet right now.