Wow! Sorry about your loss, John. When I first saw the post and pics, my first thought was AI.
Since Russ mentioned his Beagles, I just gotta add that I've had Beagles for years. Had some pups flown into from IA several years ago from Field Trial Champs and were the best I've ever had. But Buck did kill a whole slew of chicks one time. My own fault. I put a bunch of chicks out in the sun in an open brooder because it was a really nice day. Then I got busy doing stuff and mowing and didn't even think about it until I saw him run down the hill with his jowls full and two little feet flopping out the front of his mouth. I couldn't really do any thing as it was my own fault and I'm pretty sure that he was just curious and they probably freaked out which caused him to try and pounce on them to calm them down.
My Beagle, Buddy, that I have now is from Field Trial Champion blood too. You would not believe how much of a guardian dog he's turned into. The good news is he chases the coyotes off ever single day on this place. He's saved a bunch of my birds no doubt because they go under the fence and roam all over. I lose one ever now and then but he's really a good protector. The bad news is twice I've had him 20' or less from a cottontail and he just stands there and looks at it!!
I never got around to getting him started on rabbits and I'm not sure I want to now because I'd like to see the population of cottontails get better and I'm wanting to and some New Zealands and/or Giant Flemish to the place but don't wanna do cages.
Anyways, again, sorry John. I tell folks all the time that dogs kill more chickens ever year than anything else. Sorry to see you had to experience that.