It happens. It is the natural way of predator and prey. Try not to feel bad. I lost almost all of my flock 3 times to dogs. I kept their house secure but they free ranged during the day. The best thing for them during the day is a couple of good roosters. I had two that would split them and go...
Possums can get in the tiniest holes so make sure the hen house is secure. This is your number one priority. The tracks in the third pic are from a fox or dog like creature. They can not retract their claws. Racoons have "thumbs" and their track is somewhat similar to possums and look like a...