http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2711323
CLICK ON THE ABOVE LINK TO READ THIS 26-PAGE PAPER
DO BACKGROUND CHECKS ON PRIVATE GUN TRANSFERS HELP STOP MASS PUBLIC SHOOTINGS?
There is not one mass public shooting that occurred over that period where these checks would have prevent from occurring.
By John R. Lott Jr. – Crime Prevention Research Center – January 2, 2016
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2711323