The FBI says the number of shootings in which a gunman opens fire on a crowd of people has increased in recent years. The bureau released a report analyzing 160 mass shootings between 2000 and 2013. The report focuses on what the FBI calls “active shooter incidents,” or cases in which a gunman tries to kill multiple people in a confined space. According to the report, an average of six shootings occurred in the first seven years that were studied. That average rose to 16 shootings in the last seven years of the study. Examples of the killings studied include the 2012 deadly shootings at a movie theater in Aurora, Colorado and at Sandy Hook Elementary School in Connecticut.