1. U.S. Department of Justice, Active Shooter Incidents in the United States in 2018, 2019. [Online]. Available: https://www.fbi.gov/file-repository/active-shooter-incidents-in-the-us-2018-041019.pdf/view.
2. J.P. Blair, K.W. Schweit, A study of active shooter incidents in the United States between 2000 and 2013 / Blair, J. Pete, and Schweit, Katerine W.,” 2013, [Online]. Available: https://zeus.tarleton.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&db=edsgpr&AN=gprocn891206425&site=eds-live%5Cnhttp://www.fbi.gov/news/stories/2014/september/fbi-releases-study-on-active-shooter-incidents/pdfs/a-study-of-active-shoot.
3. US Department of Justice, “Active Shooter Incidents: 2000-2018,” 2019, [Online]. Available: https://www.fbi.gov/file-repository/active-shooter-incidents-2000-2018.pdf/view.
4. . U.S. Department of Homeland Security, Active shooter: how to respond educational booklet, 2008. [Online]. Available: https://www.dhs.gov/publication/active-shooter-how-to-respond.
5. Active Shooter: Preparing for and Responding to a Growing Threat;Doss,2015