I am TRULY sorry to hear that. I just lost my dog last year, it was a heartbreaking and truly painful experience that really wounded me. I know how hard it can be when a dog you love more then just an "ordinary pet" leaves you. Its never EVER an easy thing to experience
never.
My deepest sympathies and comfort, he looked like a happy/friendly dog too. Take comfort at least knowing he's not suffering any more aches or pains like that.