I caught one last night. You might be right that there is another, but I'm not sure. Once they get into a killing frenzy, they can pretty much wipe out a flock pretty quick. I'm going to set the trap again and see if anything stops by for a look see. I have the livers from our recent chicken butchering for fresh bait, so that should bring them in.
Is your fence a DC or AC powered fence? Do you use a fence charger?