Walmart, the US's largest retailer, announced on Tuesday that it will stop selling ammunition for assault-style rifles and handguns, one month after a gunman walked into an El Paso, Texas, Walmart with an AK-style semiautomatic rifle and killed 22 people.

Walmart said it will stop selling the ammunition after selling all its current inventory for assault-style rifles and handguns.

The move is expected to reduce Walmart's share of the nation's ammunition market to 6 percent, from 20 percent. Walmart said last month that it accounted for about 2 percent of the nation's firearm sales.

"As a company, we experienced two horrific events in one week, and we will never be the same," Walmart Chief Executive Doug McMillon said in an email to employees Tuesday. "Our remaining assortment will be even more focused on the needs of hunting and sport-shooting enthusiasts."

Walmart had stopped selling the type of assault-style rifle that was used in the El Paso shooting several years ago, but McMillon said the retailer recognized the need to do more "to make the country safer."

At least four Democratic presidential candidates called on Walmart to stop selling guns after the mass shooting in El Paso.

"The weapons they sell are killing their own customers and employees," Senator Elizabeth Warren of Massachusetts wrote on Twitter. "No profit is worth those lives. Do the right thing — stop selling guns."

Walmart ended the sale of handguns in all stores except those in Alaska over two decades ago but on Tuesday said it will now stop in the state as well.

Walmart also said it will no longer allow shoppers to carry firearms openly inside any of its 4,700 US stores. Shoppers with concealed-carry permits can continue to carry guns, the company said.

McMillon said the company has no plans to discontinue all gun sales, adding that it has a long history of serving hunters and that founder Sam Walton was an avid hunter. Walmart will continue to sell long-barrel deer rifles and shotguns and much of the ammunition for those guns.

"I'm a gun owner myself," Mr. McMillon said. "In a complex situation lacking a simple solution, we are trying to take constructive steps to reduce the risk that events like these will happen again," he said. "The status quo is unacceptable."

The Associated Press and Reuters contributed to this story.