Killer came back and buried them in the shavings - what does that?

A traumatic night. Around 2am we heard the hens screaming for their lives. By the time we rushed outside, two hens were dead in their yard -one a full size girl and one a bantam. Their necks were bitten. We locked up the others, but the predator returned in the night and buried the two dead hens in the shavings in their yard. What on earth would do that? It must be planning to return so of course we will spend the day strenghtening our defenses. DH thought he saw something grey when we first went outside. Cat? Raccoon? Possum?

What do you think?
Sad hen Mama

 

Thanks for your responses. The entry into the yard involved some ripping of material and the agility to climb up about 6 feet of fencing. And then to quickly return as soon as we returned to the house. We're in a suburb and have raccoons, possums, coyotes and possibly bobcats or mountain lions (although we've never seen either of these last two in our yard before.) Probably not a bear though.