One of the first people to bring up the idea that Mr. Mateen could have been gay was his ex-wife, Sitora Yusufiy, who, a day after the massacre, told The New York Times that her former husband often made angry comments about homosexuality.

“If you know anything about psychology, you know that people that have a really, really strong resentment or above-average hate toward something, it’s because deep inside that’s what they truly are,” she said in an interview at her home in Boulder, Colo. “In Islam, it’s true that there is very low tolerance for homosexuality. He may not have been able to be himself.”

But she added that she was speculating, and that there was nothing in their intimate life on which she had based that hunch.

Several men later came forward to tell other news media outlets that Mr. Mateen was a regular at Pulse. (Two of them, female impersonators who perform at the club, declined to comment for this article, though, saying the focus ought to be on the victims.)