1. A Columbine Site. (n.d.). Columbine 911 calls. Retrieved from http://www.acolumbinesite.com/911/
2. AASA. (2019). ABC’s of School Safety. Retrieved from http://www.aasa.org/content.aspx?id=7354
3. Abramson, A. (2018, February 21). President Trump suggests arming teachers during listening session with school shooting survivors. Time. Retrieved from http://time.com/5169534/donald-trump-arm-teachers-listening-session-school-shooting/
4. Aguilar, J. (2019, April 19). 20 years after Columbine shooting, little has been accomplished on gun control. The Denver Post. Retrieved from https://www.denverpost.com/2019/04/14/columbine-high-school-shooting-gun-control/
5. Alamez, T., McMahon, P., & Geggis, A. (2018, June 1). “That’s crazy boy.” School watchman recognized but didn't stop shooter before Parkland massacre. Sun Sentinel. Retrieved from https://www.sun-sentinel.com/news/crime/fl-florida-school-shooting-campus-monitor-20180619-htmlstory.html