Last year I had my very first broody hen. She was sitting on eggs when I heard a big ruckus coming from their pen.. Went in and found her under the nesting box in the grips of a rat snake.. He was after eggs. Killed him, then when the chicks were a week old, found her dead one morning and all...
I keep the rat and mice population down with Ramik.. Or you could make a bucket trap (with water in it).. Rats and mice attract rat snakes.. I also collect eggs at dusk so as to not leave enticements. I've killed a half dozen rat snakes that got caught up in the deer netting on the tops of...
Might I suggest you read some threads in the predators area. Here's just one of them.
https://www.backyardchickens.com/threads/opossum-a-deadly-threat.1505711/post-25240550
I don't know about Mass, but here in AL we coon and possum hunt all the time. Raptors are another matter as some are on the endangered list. Check with local Fish and Wildlife folks.
I hate to say it, but the best thing you can do is feed him lead! Possums have killed 3 of my chickens and when I find them, they go the way of the bullet. You are very mistaken about them not normally hurting chickens. It's not pretty when the do it either.