Thanks for the responses. Can't be a hawk as their run and coop are both covered and there were no holes made anywhere. They don't free range, ever.
I don't know where the injury happened, but their coop is solid wood/metal on three sides. The fourth side is open for air flow but is covered by the solid wood door (when closed) and the rest is that thick metal square wire which is then covered by chicken wire on top of that. I checked several times and had DH check when he got home and we can't find any holes in the run or coop that have been dug or torn. We do have opossums here and maybe a small one found a way in somehow, that's a thought.
We have 15 (well, 14 now) RSLs in that coop/run and based on those per chicken calculations, the run has enough room for 30 full sized chickens and the run for 35, so I don't think it was a crowding/boredom attack.
Thanks for the ideas, keep them coming!
Any ideas on the live chicken? Could she be molting for the first time? I was told they wouldn't molt until next year, but maybe that's not true? They don't seem to have been ripped out from what I can tell.........