There's more to the story. Gun control regulations touted in the WSJ article are so pooly enforced as to disqualify their effect on viloent crime in general, and mass shootings in particular. Consider this from a more balenced article, written by a gun rights advocate:
http://www.forbes.com/sites/larrybe...-the-myths-promoted-by-the-gun-control-lobby/The Brady lobby is upset that there has been no progress in leveraging tighter gun control legislation following the shooting January 8, 2010 rampage that killed 6 people and injured 13, including Democratic Representative Gabrielle Giffords. That tragic incident raised serious questions about background checks after it was determined that the accused shooter, having previously exhibited erratic behavior, legally purchased the weapon he “allegedly” used from a store.
The National Rifle Association clearly agrees that guns should not be sold to individuals found to have serious mental problems, although many states fail to provide mental health records to the federal computerized background check system. According to a November, 2011 report by the Mayors Against Illegal Guns (MAIG), 23 states have shown “major failures” in complying, and four (Alaska, Delaware, Idaho and Rhode Island) submit no records at all.