Mink, unless chickens really small, then weasel possible. Fox / Coyote can clear fences and will take at least some carcasses out and I doubt they would cache carcass on sight. Raccoon can do mass kills but I have not seen them bury carcass. Raccoons climb fences well and do maul head and neck of struggling victims. The mink and weasels can do make mass kills (surplus killing) and the former at least will bury some prey items. Opossums not likely to do a mass kill unless trapped in a barrel with a bunch of chickens.
Raptors not going to bury carcass.
X2......Mink......and for the exact same reasons.
BTW, entire flock of how many? A flock of 2 is different than a flock of 20.