My FIL had a mule that was as crazy as a loon, when you were in the pasture you ALWAYS kept an eye on him and never let him get in your blind spot.
Never could break it from wanting to hurt you if it could, it went to the great glue factory in the sky via the local auction house after it bit my MIL one too many times.
I forgot to mention it was a miniature mule as well.