Might want to read some of these post that others have posted about losing chickens. It might give you some ideas. Hope you get to the bottom of it before you lose...
Hawks, buzzards, or vultures probably wouldn't or couldn't eat the feet and legs. Hard for me to believe a coyote or fox came in there with all those chickens going crazy then killed one and stood there and ate it. I really believe either a fox or coyote would have scooped one up and ran off...
My thinking is a fox or coyote would have carried the entire bird away to a safer place to eat. I doubt a coon because they work mostly at night. Also they like to kill more than one. Wouldn't rule out coon or coons but still think its unlikely a coon attack. Hawk for sure a possibility. A hawk...