I found 4 of the chickens alive later this evening. All are wounded, one I don't think is going to make it. She has deep wounds on her back, she's unable to get up on the roost, and isn't supporting her weight with one of her legs. I put Vetericyn on her wounds.
I think we also saw the culprit. It looks like a 45-50 lb cat. My daughter and I just happened to look out my bedroom window into the back yard where we saw it stalking what later turned out to be the most gravely wounded of my chickens. All are locked safely in the coop. Of course, it was my favorite hen that was killed today. She's sitting on my shoulder in my profile picture. I am heart sick still but so happy the rest of my girls are home.