The following is an open letter to Doug McMillon, the chief executive of Walmart.

Dear Mr. McMillon,

The massacre at your store in El Paso over the weekend was a tragedy.

So were the shooting deaths, days earlier, of two Walmart employees, at a Walmart store in Mississippi. So, too, was the mass shooting early Sunday in Dayton, Ohio — and the multitude of others in recent years.

It is clear that this country is suffering from an epidemic that law enforcement and politicians are unable or unwilling to manage.

In the depths of this crisis lies an opportunity: for you to help end this violence.

You, singularly, have a greater chance to use your role as the chief executive of the country’s largest retailer and largest seller of guns — with greater sway over the entire ecosystem that controls gun sales in the United States than any other individual in corporate America.