In that case, Walmart's mandatory "active shooter" program may have helped save lives. Employees there acted quickly when a disgruntled colleague allegedly killed two co-workers and injured a police officer.
"I feel confident in saying that it did (help) in Southaven," said Walmart spokesman Randy Hargrove in a phone interview, adding that employees guided other associates and customers to the right exits and out of danger.
It is not yet clear whether the mandatory active-shooter training completed by all Walmart employees helped save lives in El Paso.
With its doors open to shoppers often late into the night in towns across the country, Walmart stores have seen their fair share of confrontation.
"You can never predict violence, which is why we focus on training and preparation so seriously," Hargrove said. "No business or retailer is immune."
Walmart employees complete an active shooter training program during orientation and afterwards on computers four times per year.
That level of training is believed to be unique in the retail industry, Hargrove said. Walmart is the world's biggest retailer and the largest U.S. private sector employer.
The training had been required once per year but became quarterly in 2017, the same year separate shooters killed 58 people at a music festival in Las Vegas and 26 people at a church in Sutherland Springs, Texas.
"We have evolved how we are dealing with different crisis situations through the years," he said.
In 2014, Walmart announced its partnership with Texas State University to implement its "Avoid, Deny, Defend" training for civilians to respond to active public threats, rolling out that program in 2015 to employees.
"We know our program works," he said. "Naturally, any time there is a situation, you're going to look at what you're doing from every different angle."
Other major U.S. retailers did not return calls seeking information about their security programs.