Hi Shauna,
I'm so sorry you have to deal with this very sensitive matter. How is your eye? You know what, maybe when you were petting him, he was sleeping and maybe in a dream and it just startled him and he reacted because he was "out of it"? For him to have never done that before, and he has always been a sweet gentle dog, it doesn't make sense that he would do this. Does it? Is it an option to just watch him over the next few days, or weeks and see if he gets aggressive again, and then if he does, you can make the decision then? It would be such a shame to put him down, if he really didn't mean to do that, and was just in a dream state or something. I really hope you all are okay.
Lots of hugs,
Ginny
I am a total animal lover myself. Hearing this breaks my heart. For you all, who love him so much, and for him too.....