It looks like something a cat would do, they have a very strong natural prey drive and will kill almost anything they can catch. A cat that lives in the house and is fed well usually won't eat what it kills and whatever killed this bird was definitely not interested in eating it. Also, the cuts are around the neck, cats will go for the neck instinctively when hunting. It is definitely not a dog kill, although they are in the same boat as the cats, they have a strong instinct to catch and kill anything that runs from them, and a well fed dog usually won't eat what it catches. I know it is not a dog though because a dog would have chewed it up and thrown it around like a toy after catching it, also if a dog grabbed that bird by the head it would not have any head left after the dog was done with it. Just because it was a cat doesn't mean it was your cat, lots of cats actually do really well around adult poultry. It could have been someone else's cat that they let free range.
It is not a hawk or an owl, even though some can't lift a large chicken that does not stop them from plucking and eating one. Also, judging by the size of this pullets comb I would say she is pretty young and a large hawk or owl could definitely lift her. A red tailed hawk can lift up to 10 pounds off the ground and can carry away most chickens, and if a hawk can't lift a prey item it will dismember it and carry it off piece by piece. Raptors do not kill for fun, nothing does. Owls, especially, will stick to a large kill and come feed off of it for many days during the colder months, they won't even bother dismembering it to carry it away, they just leave it in the snow then come in for a snack when they feel like it.
