Study: The U.S. has had one mass shooting per month since 2009 February 2, 2013 · Leave a Comment … So how much do we actually know about mass shootings and the people who commit them? A new study commissioned by Mayors Against Illegal Violence tries to add some much-needed detail. [cont.] Brad Plumer, Washington Post Share:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Reddit (Opens in new window)Click to email a link to a friend (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Tumblr (Opens in new window)Click to share on Pinterest (Opens in new window)MoreClick to print (Opens in new window)