I'm lvl 26 now and I've had the same horse since I first bought her outside of Whiterun. I was travelling in the Northern region of skyrim around Hsaarik Head before I encouted 3 wolves and 2 bears.. As much travelling as I'd done with that horse, she was backed to an ice-capped ledge and mauled by one of the bears, sending her falling down into the ocean.
As for the pack that attacked us. then didn't enjoy my lightning storm.. When I was finished with them, each of them, one-by-one, was tossed over the ledge to join my long gone companion. She will be missed.
