The more I read about Omar Mateen, he is an injustice collector/injustice creator that harbored grudges for all his life. He would also be vicarious as terrorists are that. Most terrorists are injustice collectors, mainly vicarious injustice collectors.
On Wound Collectors
https://www.psychologytoday.com/blog/spycatcher/201509/wound-collectors
Identifying The Next Mass Murderer—Before It’s Too Late
https://www.psychologytoday.com/blo...ntifying-the-next-mass-murderer-it-s-too-late
The Dangerous Injustice Collector: Behaviors of Someone Who Never Forgets, Never Forgives, Never Lets Go, and Strikes Back!
http://online.liebertpub.com/doi/pdf/10.1089/vio.2014.1509
Psychology of Terrorism - National Criminal Justice Reference Service
https://www.ncjrs.gov/pdffiles1/nij/grants/208552.PDF
Injustice collectors tend to be complainers as they always have some grievance. They are highly negative in nature. An example of an injustice who always complains.
Websleuth Radio Interview Of Tina Meier describing Lori Drew
http://www.blogtalkradio.com/websleuths/2013/09/30/tricias-true-crime-radio-adult-cyber-bullying
At the 20:40 mark, Tina Meier's description of Lori Drew is what describes Syed Farook, Tamerlan and Dzokhar Tsarnaev, Abdelhamid Abaaoud, or Mohamed Atta. This would very likely apply to Omar Mateen. They are very unhappy and resentful as they are extremely envious of others. It is always about them as they are not pleasant people to be around. They are professional victims that rage at the world. They are perpetual victims and feel like society marginalizes them. They blame everyone else, but themselves.
WEB OF LIES: Deadly Cyberbullying Case of Missouri Teen Unravelled Tonight on ID (Video Preview)
http://tvruckus.com/2015/01/28/web-...-teen-unravelled-tonight-on-id-video-preview/
I have seen that show on Investigation Discovery. Tina Meier said that Lori Drew had problem fitting along with her daughter. Something you hear often with terrorists and rampage killers. This suggests injustice collectors have trouble fitting in. They said that about Syed Farook and Tashfeen Malik, Kouachi Brothers, 9/11 Terrorists, Elliot Rodger, Adam Lanza, Seung-Hui Cho, and Dylann Roof.
Insights into Isla Vista Shooter Elliot Rodger
http://www.independent.com/news/2014/may/24/insights-isla-vista-shooter-elliot-rodger/