Our Deepest Condolences Lisa and Hershey... :no:
Mike took a look at the wounds, and thinks that perhaps you have a young/small Black Bear in your immediate vicinity. He ruled out large cat or coyote from the looks of the wounds. You might want to make sure that you bring in your other horses at night, he has had a taste of blood now, and knows where to get more. Bears eat grasses and dandelions the first month out of hibernation, then they start looking for meat, and that would put it right about this time of year.
Hope it is not, but Mike is a very good hunter/tracker, and that is what he said it looks like... We are so sorry for your loss Lisa...
Nancy & Mike