There is a famous quote, which I tried unsuccesfuly to find that, goes something like " if coyotes did this they did it with scalpels! followed by the response that said “if surgeons did this they did it with their teeth!”
It is normal, predators, flies, an decomposition. “They were completely drained of blood!” no they weren’t, blood clots up and will no longer flow from a dead animal.
I see that I addressed this in the Carol quote linked to above. Under my original user name! My how time flies. Like flies on a dead cow.