When a gunman killed four people and wounded a fifth at a Southern California office building last week, news outlets, over and over, called it the third in a string of mass shootings. “The violence in the city of Orange was the third major mass shooting in just over two weeks,” an Associated Press story published on chicagotribune.com read. “Last week a gunman opened fire at a supermarket in Boulder, Colorado, and killed 10. A week before that, six Asian women were among eight people killed at three Atlanta-area spas.” No mention of Chicago. In Sunday’s New York Times, Nicholas Kristof wrote …