I asked them what they meant by threatened. They whistle, they told me. At sunset, just as the sky darkened, MS-13 gangsters would come to the border and whistle at them.

Sure enough, 30 minutes later, the whistling began.

It was chilling, in some ways as terrifying as what was to come — shootouts, armed raids and clandestine meetings with the same MS-13 leaders trying to kill Casa Blanca members.

Terrifying because in that moment I realized how completely surrounded these children were — and I say children because most were in their teens, scarcely old enough to shave. I knew that to tell their story I needed to be in the community, not traveling between a hotel and the neighborhood. I wanted intimacy and proximity: to be there all the time, to bear witness to events as they unfolded. And I wanted to reflect the realities of life in Rivera Hernández through the voices of those living there — gangsters, residents, shopkeepers and families.

So I asked the pastor if Tyler Hicks, the photographer, and I could live with him for the weeks we were in town. At first, I didn’t know what a major character he would be in the story; I assumed he would help us here and there, but that my time would be spent with Casa Blanca members. And he lived just a few blocks away, in 18th Street territory.

But the more time we spent there, and in particular after the first shootout, where I witnessed an MS-13 gunman sow terror in the neighborhood without even flinching, the story began to center on the pastor. He was taking action — risking his life to intervene.

And so more of my time was spent by his side, reacting to every event described in the piece. All told, we spent about three weeks together.

I witnessed firsthand every scene in the story — except for the raid at the home of Fanny, who provided refuge to Casa Blanca members. (I arrived only moments after the gunmen left.) I was there when an MS-13 gunman shot up the neighborhood in broad daylight; when Mr. Pacheco tracked down the MS-13 leader to plead for the lives of Casa Blanca members; when he sat down with the MS-13 soldiers who were tormenting the neighborhood; when a representative of Casa Blanca finally sat down with MS-13.