Yes, I saw that earlier.
A lack of blood suggests that he was not killed by chickens. It could have been by a predator that just broke his neck, or by a disease. I'm thinking disease, as you posited originally. If it's a disease, you should probably figure out what so that it doesn't spread to the rest of the flock. If it was a predator, you need to secure your coop.
But something pulled out those feathers, and that suggests predator. An animal will grab feathers, only pull out a few, and might account for the scattered feathers in the picture if they weren't there before today (and they do look fresh and new.) Hens tend to pull them out over a period of time, slowly escalating. If those feathers weren't there before today, then it might have been a predator that did it.
Are your girls acting "shocky?" That would indicate a predator. Are you missing any chickens? (I realise that counting 36 can be difficult, but are you sure you aren't missing any? I didn't see a post where you said you did a headcount.)
I'm sorry if I'm being a "loud" poster, or annoying.