It's too bad you didn't have a camera with you. There are a few cougars that roam this area and one of our neighbors has had a calf killed by what he says was a black panther (cougar or leopard?). He said the damage to the calf is unmistakeable — a torn out abdomen. There are plenty of stories around here about black panther. We saw a regular cougar cross the main FM road into town early this spring. So why not a black cougar.
Our USDA and state park biologists may not know what is and what is not here or what these animals can do. I recently lost a newborn 55 lb. heifer to a mixed flock of Black Vultures and Caracaras. The ranger with whom I spoke insisted they are scavengers only, but these guys killed my heifer and have been pecking at my other newborn calves. My DH has seen Caracaras circle the tractor and pick rabbits off the ground as they run away from the moving tractor.