I had to put up deer fencing for my free range chickens due to free range dogs.
You have no proof the dogs did it and since you have zero predator proofing (fence, hardware cloth, and other protection), you can't really blame the dogs since a plethora of different predators could've done this. You would need actual proof the dog did it, like pictures or videos.
I would call animal control if you see the dog that's about the only legal thing you can do since you have zero proof it's attacking or speak with your neighbors to see if it's their dog. They might not even own the dog, but just say "I saw a (whatever color the dog is) and it was hassling my chickens, is this your dog or do you know who owns it" don't accuse them of owning it just ask of they do own it or know who does.