It looks like between the two of us we have unraveled the reason for his mad act. Self hatred, anger at those who look like him and homosexual feelings/acts? that could only be redeemed by martyrdom and killing copies of himself.
I suspect fewer psychological overtones. Self redemption yes. Self- hatred? not like a westerner would experience it. A non Moslem with these contradictions feels boxed in, no way out and kills himself in despair or himself and others. The Moslem always has an outlet. He does not feel he is anihilating himself. He is going straight to Paradise to relax in the shade of trees where rivers flow. He is doing something positive for Allah and for himself. He may also think that Allah made him the way he is in order to kill a lot of homosexuals. Moslem belief in Fate is beyond most non Moslems’ comprehension. Allah immediately wills everything, every motion of every grain of sand. Cause and effect are not really concepts outside of what Allah wills at each moment. Mateen buys guns and does his deeds because Allah wills that he do these things. He may or may not hate what he is, himself, and probably doesn’t.