My dad was a coach in several different high school sports over the years, and dealt with a lot of crazy parents. But the worst of all was one who threatened to kill him for not picking his kid (who was not good at all) for the team. Well, it wasn't just a one time tirade, as he began stalking and harassing our family by phone -- like calling and claiming to be the coroner's office. This went on for a while and my folks were hoping he'd run out of steam, but he didn't. They finally had to involve the police, who had a little "chat" with him. Problem solved!