Walmart, scene of two recent gun horrors, is under pressure to use its corporate power to help crack down on the sale of weapons in the US.
The country's biggest retailer, often cited as the biggest gun seller, has faced criticism before over arms sales.
But after a multiple shooting at a Texas store, and the death of two staff at a Mississippi branch, critics say Walmart has a responsibility to act.
The killings are in addition to another mass shooting, in Ohio, at the weekend.
Igor Volsky, founder and executive director of Guns Down America, said the killings at Walmart put the retailer under an obligation to take a lead.
"The El Paso [Texas] shooting happened in their store. They have a responsibility to go further," he said. Walmart could use its political and lobbying clout to force change, he added.
Previously, Guns Down led a successful campaign calling on logistics giant FedEx to stop offering discounts to National Rifle Association (NRA) members.
Another organisation, Moms Demand Action for Gun Sense in America, said Walmart must stop letting shoppers walk into stores with guns. A number of retailers have such policies, including Target and Starbucks.
Kroger-owned Fred Meyer stopped selling guns in 2018, and the same year, Dick's Sporting Goods ended the sale of assault weapons and raised the minimum age to 21 for gun purchases.
Other pressure groups called on Walmart to use its vast resources to invest more in security, training, and education. These groups have been joined by high profile individuals. Actor and activist Alyssa Milano said it was time for Walmart to show leadership.
And one of America's leading writers on corporate America, the co-creator of the hit TV series Billions, Andrew Ross Sorkin, issued an open letter to Doug McMillon, Walmart's chief executive.
"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."
He said Mr McMillon should join forces with powerful chief executives who have expressed dismay at America's gun violence, including Apple's Tim Cook.
Walmart has also faced a huge social media backlash from people using such hashtags as #walmartshooting," "#boycottwalmart," and "#guncontrolnow."
It is not the first time that gun-control campaigners have called on Walmart to act. In 2013, a month after a gunman in Connecticut shot dead more than 20 people at a school, nearly 300,000 people signed a petition urging Walmart to stop selling assault weapons.
It was another two years before Walmart ended such sales.
The retailer has yet to respond to a BBC request for comment.
But according to a spokesman quoted in the Washington Post, Walmart has no plans to change its policies on gun sales and in-store carrying.