How far is the coop from your house? - Nearby activity can give us a better idea: A kill during the day by a four-legger would be a bit unusual (except for a dog). Bobcats are pretty stealth, I think highly unlikely during the day. Foxes not as stealth as a bobcat, but a daylight kill seems unlikely. Coyotes can be quite brazen, and I wouldn't doubt a daylight kill; but they're smart and sensitive to noise, so they're usually more of a night-time killer. I can't tell from the picture, but if there is any kind of a trail of feathers, it's probably a four-legger. They will carry off their kill to the pack or the den.
If there's no trail of feathers (Make sure you look around carefully, i.e., nearby fences may have fur of the killer on it.), it's probably a hawk. They'll peck at the chicken's head first, kill it, and then eats what it can. They'll carry off what they haven't eaten, just like the four-leggers. Hawks come in all sizes, and the larger ones can carry off a grown chicken, no problem.
I've rarely seen any blood or body parts left behind by any of the above-mentioned chicken killers, unless the kill is interrupted. All of the above are killers of opportunity, and if the kill was recent (spring), remember, they have babies to feed too. Therefore, what's "normal" is no longer normal when there's more mouths to feed. Whatever it was, it will probably be back.
I'm very sorry for your loss.
