New York (CNN Business) Last year, Dick's Sporting Goods ended the sale of semi-automatic, assault-style rifles and high-capacity magazines after a mass shooting in Parkland, Florida, killed 17 people. It also raised the age for purchasing weapons from 18 to 21.

, despite a history as a seller of hunting weapons that goes back to its origins, has also shifted its gun sales policies in response to high profile shootings. It stopped selling assault rifles in 2015 and raised its minimum gun purchasing age to 21 last year after the Parkland shooting.

America is again confronting shocking illustrations of the devastation of mass shootings, and advocates devoted to ending gun violence and a wave of angry people on social media are calling on Walmart to do more.

As the country's biggest retailer, Walmart remains a major seller of firearms. In the past week, it has been the scene of two shootings. A white nationalist killed 20 people inside a Walmart store in El Paso, Texas, on Saturday. Last Tuesday, two employees were killed in a shooting at a Mississippi Walmart

The kind of gun used in Saturday's attack has not been sold at Walmart in years. But now that gun violence has hit Walmart's own stores as customers were back-to-school shopping with their kids, many are wondering whether the company will take additional steps to limit firearms sales.

"As an employer and a place where a huge population of very diverse people shop, it's in Walmart's interest to reiterate what it's going to do to ensure that it's employers and its customers are safe," said Kris Brown, president of gun violence prevention advocacy group Brady.

Social media users call for Walmart to end sale of firearms

The company faced hundreds of calls on social media to stop selling guns altogether. On Saturday, Walmart tweeted that the company is "in shock" after the shooting and is "praying for the victims, the community and our associates, as well as the first responders." Many responded to that message saying that as a major gun retailer, the company should not be shocked and urged it to change its policies.

"Hey @Walmart! This would be a great opportunity for you to take a true leadership position and stop selling guns," actress Alyssa Milano said in response to the company's tweet.

Venture capitalist and entrepreneur Chris Sacca had a similar response: "Hey @Walmart, maybe you could, hmm, I don't know, stop selling guns?"

Hey @walmart, maybe you could, hmm, I don't know, stop selling guns? https://t.co/DqsbR7PnJ7 — Chris Sacca (@sacca) August 3, 2019

Such a step could make a significant difference — studies show that cutting down on the availability of firearms can reduce gun violence.

Others on Twitter called on the company to stop allowing open carry of firearms in its stores, something the company says it does in states such as Texas where open carry is legal.

Walmart does, however, already have what many gun violence prevention advocates consider strong gun safety policies that go beyond federal requirements: it doesn't sell assault weapons, it doesn't sell to people under 21, it requires background checks and it no longer sells toys that resemble assault rifles.

Even if it doesn't change its policies, many think Walmart is positioned to push lawmakers to enact tighter gun restrictions.

"There's a role to play in leadership and advocacy here," Brown said. "Walmart's already implemented these policies on its own ... They've done it because they're concerned about public safety if they don't. So why wouldn't they say from a national perspective, if we want people to feel safe, these steps should be taken more broadly?"

And while Walmart is a major gun seller, there are many places where people can buy guns. Brown said the company should encourage other retailers to follow its lead in implementing safe firearms sales policies.

Walmart could also play a role in educating its customers on gun safety, said Texas Gun Sense President Ed Scruggs. Especially in rural communities, Walmart stores act as de-facto community centers that Scruggs said would make them sensible homes for education programs.

"We have a problem in Texas with children and teenagers accessing firearms that are not properly stored," Scruggs said. "They could perhaps have free courses in the store on gun safety or promote the use or trigger locks or have big sales on gun safes. To reach out to the community may seem like a small thing but they have an opportunity to reach a lot of people."

Navigating social issues in corporate America

Many companies became publicly involved in the fight against gun violence after the shooting in Parkland last year. Denim brand Levi Strauss pledged $1 million to gun violence prevention groups and helped to form a coalition of business executives working on gun control. The founder of shoe brand Toms committed $5 million to gun safety organizations and launched a postcard-writing campaign urging Congress to pass universal background checks. Bank of America pledged to stop lending to makers of "military-style firearms" used by civilians.

Dick's Sporting Goods DKS CEO Edward Stack has also been vocal about his decision to change the company's gun sales policies after Parkland, at one point noting he didn't care what the financial implications would be.

"You know everybody talks about thoughts and prayers going out to them. That's great. That doesn't really do anything," Stack said on CNN last year. "We felt we needed to take a stand and do this."

Dick's has pulled gun sales entirely from more than 100 of its stores, and suggested that trend may continue.

Public statements like these do make a difference, said Shannon Watts, founder of gun safety advocacy group Moms Demand Action. And it can be faster and easier for big corporations to enact a new policy or public position than for lawmakers to draft and pass a new law.

"To have Walmart join the coalition of companies working actively on this issue, making it a priority in their foundational platform would send a strong signal," Watts said. "Companies have a role to play. When lawmakers don't protect their constituents, companies have a responsibility to protect their customers."

Walmart's immediate focus

For now, just about 36 hours after the attack, Walmart's policies remain the same, according to company spokesperson Randy Hargrove. Hargrove also pointed out that the company has provided quarterly active shooter trainings for all employees since 2015, and that all of the staff at the El Paso store that was targeted Saturday had been trained.

"We continue to be devastated by the loss of lives, and right now our focus is on supporting our associates, our customers and the El Paso community," Hargrove said.