Wikipedia: On March 13, 1919, someone stating that they were the 'Axeman of New Orleans' sent a letter to a newspaper threatening to kill again at 15 past midnight on March 19. He said, however, that he would not kill anyone who went to a jazz show. On the night of March 18/19, all of the jazz clubs were filled to capacity, and professional and amateur jazz bands played in houses and parties all over the city. No one was killed that night. In the words of my dear friend who shared this with me, f*** Facebook events, this guy was an event management genius.
(Think outside the square.)