I went away for 4 days & had a friend watch the chickens. She said she had no problems.
We moved the birds to a new grazing area yesterday, and got them all settled in.
When I open the door this morning, I didn't notice anything off in the coop (morning grogginess hadn't worn off yet)
Less than an hour later I go into the coop and find one of my ladies, dead.
No coop damage. The only opening in the coop is small enough for a young snake to squeeze through, so I'm not convinced it's a snake.
I plan to do an autopsy after posting this. I'll let y'all know what I find.