I had a similar attack this past summer, not long after I built the new coop. The predator killed all of the chickens in a similar manner. Most still had heads attached but I found no signs of wounds. Perhaps due to my failing vision. I suspect it was an ermine of some sort.
Since that time, I wired the perimeter of the coop with HW cloth and the pullets have been safe.
I didn’t catch the weasel two nights ago. He checked out the coop and couldn’t get in. Last night he returned to a new coop (my largest 10x16’) that I thought was secure. It is now war on weasels. I’m moving 30+ birds to other coops tonight. Putting two sacrificial roosters in a “hopefully “ weasel proof cage in the middle surrounded by traps. Today will be spent outside in the yuckky weather going over all the other pens to be sure I didn’t miss something.