http://usliberals.about.com/od/Election2012Factors/a/Gun-Owners-As-Percentage-Of-Each-States-Population.htm
https://ucr.fbi.gov/crime-in-the-u.s/2011/crime-in-the-u.s.-2011/offenses-known-to-law-enforcement/expanded-offense-data
https://ucr.fbi.gov/
https://www.fbi.gov/file-repository/activeshooterincidentsus_2014-2015.pdf/view
https://www.fbi.gov/file-repository/activeshooterincidents_2000-2015.pdf/view
https://ucr.fbi.gov/crime-in-the-u.s/2014/crime-in-the-u.s.-2014/tables/table-16
