Exactly!The aftermath of what possums do to chickens would have you feeling much worse, I promise. When they enter your yard, kill them.
I had a possum show up in the afternoon at the waterers that are on the outside of my pens for the Guineas. By the time I went in to get the .22 and came back out it was under the porch looking all innocent. I shot it anyway as I've SEEN what they will do to chicks. It would only have been a matter of time until the one under your bush got into your pen and got the chickens.
The only 'good' possum is a dead possum. Coons are the same way. They will reach thru the fence to get to your chickens and if they can, they will kill them. I recently lost 6 eight week old chicks in one night to either a possum or coon. These chicks were INSIDE an enclosed area INSIDE my enclosed pen and something still got them.