A person that has a face that looks like a butt and is very violent. Their face (which is a butt crack) holds a knife that they bring out to kill. He also walks around not knowing where he is going due to his butthole being his eye. After the kill, he goes to the bathroom to drop a fat nuke.
Watch out for the Butt Face Killer is walking around so keep your distance or he will kill and drop a fat nuke.