Xinhua/REX/ShutterstockBy Steven Stack Mass shootings have spiked in the US in recent times. A study of FBI reports on 160 gun sprees shows they went from an average of 6.4 a year in 2000-2006 to 16.4 in 2007-2013. What’s more, two recent large-scale investigations looking at hundreds of shootings between 1997 and 2013 have documented a “clustering”...