I don't know what the circumstances were, but from what I've heard, in rural areas, those services aren't readily available and it's not that simple. I don't think I could ever do it, but I have definitely heard of owners putting down animals for a variety of reasons.
the internet is powerful. I guarantee he posts they need help with these dogs on Facebook, they would have had so many people and Orgs reach out. But, it seems he had already decided he was gonna kill those dogs before he even went there.