Free: Contests & Raffles.
No visible damage. Betting it was a dog. If you think a raccoon or fox could get to them, why do you think that a dog couldn't.
Likely a weasel or maybe a mink if you live near water. Had a weasel get some ducks and a goose years ago that were tightly penned up at night in a chicken wire cage. Made it easy access and pickings for the weasel that got mine.
don't overlook rats. A big rat will kill chickens and leave little trace.