In 2018, a small group of Texans gathered to commemorate the centennial of a massacre that unfolded 200 miles southeast of El Paso, in the Presidio County community of El Porvenir. One white witness to that shooting is quoted at length in Monica Muñoz Martínez’s book, “The Injustice Never Leaves You: Anti-Mexican Violence in Texas.”

Robert Keil entered the town with Texas Rangers and U.S. cavalry troops and ranchers investigating a cross-border raid during the Mexican Revolution. He heard the wails of women pleading for the lives of their loved ones. Then he heard gunfire, and saw “the most hellish sight that any of us had ever witnessed.” Fifteen men and boys had been marched out of the town and executed, their bodies gathered in a heap of limbs and blood at the foot of a bluff. “It reminded me of a slaughterhouse.”

As The Times reported in March, the reasons given for these extrajudicial killings varied wildly: The victims were accused of “cattle theft, murder, cheating at cards, refusing to play the fiddle … even witchcraft.”

As a candidate and as president, Mr. Trump has done much to spread a modern-day notion of people of Latin American descent as a menacing horde, devoid of humanity. At a rally in Florida in May, held after a caravan of Central American immigrants reached the United States border, Mr. Trump lamented: “How do you stop these people? You can’t.” A member of the audience shouted back, “Shoot them!” The audience cheered, and the president smiled.

The El Paso suspect dedicated a large portion of his “manifesto” to listing the weaponry he would use in his attempt to help start a race war. He said he would carry an AK-47, an assault rifle with its origins in the infantry battles of World War II.

Across the United States, police departments practice active shooter drills as they prepare to encounter such men. At our workplaces and schools, we are given instructions as to what to do when we come under fire. We are told to “run and hide.” And to “yell and fight.” “Throw items and improvise weapons,” one police department suggests.

I, personally, am not excited at the prospect of having to make one last charge against a spray of bullets. On most days, there are safer ways to fight white supremacy. We can study the beautiful and tragic story called “United States history,” for instance, and spread the message of the idealism and hope there — including the resilience of millions of Mexican immigrants and their descendants. And we can vow to learn from this past, and “yell and fight” against the demagogues whose words encourage the lonely killers among us.

Héctor Tobar ( @TobarWriter ), an associate professor at the University of California, Irvine, is the author of “Deep Down Dark: The Untold Stories of 33 Men Buried in a Chilean Mine, and the Miracle That Set Them Free” and a contributing opinion writer.

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