2015: a year in mass shootings

News reports from the scenes of mass shootings in the U.S. were all too familiar in 2015. In total, there were 372 mass shootings in the United States last year, as of the morning of Dec. 31. These shootings, quantified by the website MassShootingTracker.org as involving four or more people, killed 475 people and wounded 1,870.