We don't really know if Omar was with ISIL, or if he was an extreme homophobe. We don't know if he did this because of religious beliefs. Reports of his character are conflicting. We can assume that like other mass shooters, he was mentally disturbed. But in the end we are left having to accept the fact that he committed an evil act, for no logical reason. Several people lost their lives, and there's nothing we can do about it.
My condolences go out to the families, partners and friends of the victims.