On Friday, at least four Democratic presidential candidates, including Senators Elizabeth Warren and Bernie Sanders, called on Walmart to stop selling guns.

Federal investigators are treating the shooting in El Paso, in which 22 people were killed by a gunman who the authorities say was a white man driven by xenophobia, as an act of domestic terrorism.

In a 2,300-word manifesto that appeared online minutes before the shooting, there is a reference to Call of Duty, a first-person shooter video game franchise. But anti-immigrant language is far more prominent in the hate-filled document, which said in the second line that the attack was “a response to the Hispanic invasion of Texas.”

The day after the massacre, another shooting in Dayton, Ohio, killed nine people.

At a Walmart in Southaven, Miss., last month, a disgruntled former employee killed two supervisors in an attack that ended in a shootout with the police in the parking lot.

And on Thursday, a man with a loaded rifle and 100 rounds of ammunition walked into a Walmart in Missouri, alarming shoppers before he was detained by an armed off-duty firefighter and arrested by the police.

“We will work to understand the many important issues that arise from El Paso and Southaven, as well as those that have been raised in the broader national discussion around gun violence,” Doug McMillon, Walmart’s chief executive, said in a statement on Facebook on Tuesday.

“We will be thoughtful and deliberate in our responses, and we will act in a way that reflects the best values and ideals of our company,” he added.