The Crime Prevention Research Center (CPRC) recently released a report that indicates that from January of 2009 to July 2014 92% of all mass shootings in the US occurred in gun-free zones.
http://www.dcclothesline.com/2015/1...ss-shootings-have-occurred-in-gun-free-zones/
http://www.dcclothesline.com/2015/1...ss-shootings-have-occurred-in-gun-free-zones/