I think it is a case across the world, in murders of intimate partners, and quite often, also, between people who are associates, or business partners, the main driver being , the victim and the perpetrator know each other, most often intimately, that there is a compulsion to cause facial injuries, of a particular nature.
Some forensic psychiatrists believe this is a matter of battering the person from looking, or seeing the perpetrator, and also, it sometimes happens post mortem, going back to have another moment of defacing someone.
sorry, not a happy subject.