http://www.edweek.org/ew/articles/2014/10/29/10moore.h34.html

http://www.nbcnews.com/news/investigations/f-firearm-more-teachers-authorized-carry-weapons-classroom-n208946

http://gunwars.news21.com/2014/debate-has-changed-since-newtown-but-not-always-in-predictable-ways/

http://abcnews.go.com/US/school-shootings-columbine-numbers/story?id=36833245

http://www.self-defense-mind-body-spirit.com/average-police-response-time.html

Use these sources