Donald Trump insists that the key to stopping terrorism is having Muslims report on one another to the FBI. But Omar Mateen, the shooter who killed 49 people at a gay nightclub in Orlando, was "turned in" to the FBI.

And the person who did it was a fellow Muslim from Mateen’s own mosque.

In an op-ed published in the Washington Post, Mohammad Malik wrote that he tipped off the authorities after he had a conversation in which Mateen confided that he had been listening to the lectures of Anwar al-Awlaki, a radical Yemeni imam.

"He hadn’t committed any acts of violence and wasn’t planning any, as far as I knew." Malik wrote. "But it was something agents should keep their eyes on."

As a result of Malik’s tip, the FBI opened a file on Mateen, but eventually closed it because at the time he showed few serious signs of criminality or radicalization.

For the Muslim community in Port St. Lucie, Florida, the process unfolded exactly how Trump and his supporters argue that it should — and in fact often does: A member of the community noted suspicious behavior and turned over that information to the authorities. Still, Islamophobic rhetoric and assumptions flourished in wake of the shootings, according to Malik:

There’s so much suspicion of Islam here. The local paper published an unsigned editorial called "Leave our peaceful Muslim neighbors alone," and the comments were full of hateful lies — that the Boston bombers had visited the area, that the Sept. 11 bombers came from here, that we were a hotbed of violent ideology. None of this is true. Donald Trump didn’t create these attitudes, but he plays on them and amplifies them.

Muslim Americans do report signs of radicalization, and they do it often

The myth of widespread Muslim complicity in terror attacks has been debunked both often and thoroughly. The director of the FBI has directly refuted Trump’s claims. Gallup has reported that since 9/11, Muslim Americans have helped law enforcement prevent "nearly two of every five al Qaeda terrorist plots threatening the United States." The Muslim Public Affairs Council has developed and advocated a community-based violence prevention and intervention model.

And they have good reason for doing so. As Jennifer Williams wrote for Vox:

Not only do Muslims want to stop the direct loss of life and destruction that can result from an attack, but we also want to halt the damage to our image as a religion and a community whenever someone carries out an attack in our name. American Muslims have every reason to report suspected terrorism activity, and we're not going to stop doing it just because a few politicians say ugly things about us to win votes.

But regardless of these facts, and regardless of the relatively small threat that terrorism poses to the average American, Trump hasn’t backed away from either his proposed Muslim ban or his accusation that Muslims aren’t trying to stop terrorism.