Dozens of sets of human remains believed to belong to migrants have been recovered in the desert near Ajo, including 18 sets of remains Warren said he helped find. The fact that so many people have died near Ajo is “unconscionable to me and it requires me to act and to do something,” he said.

He leaves water and food near places where human remains were recovered, with the goal of preventing more deaths, he said. For migrants who have suffered or died there, Warren said, “Their spirit continues to dwell in that place.”

Many migrants die alone in the desert, often after being separated from their group, injured, or dehydrated, Warren testified.

“There was nobody there to witness them when they died,” he said. By serving as a witness to their death, it provides a “spiritual completion for them.”

When he finds human remains, he performs a ritual. He faces the remains, offers a “silent acknowledgment,” and then turns away, he testified.

“I kneel down and pick up two handfuls of dirt or rocks or whatever kind of soil it is,” he said. “I’ll hold that in my hands, mash it together. In my mind, that’s the act of holding that ground, holding that place in my hand, holding it tight.