What animals kill chickens in the day by ripping the vent?

Possibly a raccoon, or maybe a weasel. I don't know if you have any in the area but skunks are also known to find a way in and not just steal eggs, they will kill a chicken.

The only animal I've ever heard of taking chickens in daylight is the hawk but they do not attack the vent of the bird. A weasel will go for the area of the body that most smells like blood, head, neck and vent.