My current theory is that he had a psychotic episode. His father was described by the FBI as a psychotic. So mental illness runs in the family. Since there is currently no better explanation, I would take a wild guess that he was afflicted with a mental disorder that showed up quite suddenly. Living a normal life, and then all of a sudden, flips out and decides to go to Vegas and shoot a bunch of people.

My alternative really off the wall theory is that he didn't actually do it. He was taken hostage by ISIS or someone else who did the shooting, and then they "suicided" him and made their escape, leaving him to take the blame.

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