The first thing you should do is talk to your dad about why this happened. What triggered it? If it seems like it was triggered out of nowhere, then there may be an underlying health issue that caused this. For example, bipolar disorder, borderline personality disorder, and dementia could all be medical reasons as to why this adulteration occurred. If it occurred because he was unable to perform basic activities that he has in the past and he took out his frustration on someone else, then it may be time for him to move to an assisted living community where the workers take care of more of the daily duties.