America's largest retailer, Walmart, says it will no longer sell guns to people under the age of 21 in the wake of the Florida school massacre.
The US firm said it was also removing items from its website that resemble assault rifles, including non-lethal airsoft guns and toys.
Seventeen people were shot dead at Marjory Stoneman Douglas High School on Valentine's Day, prompting calls for survivors for stricter gun controls in the US.
In a statement, Walmart said: "In light of recent events, we've taken an opportunity to review our policy on firearm sales.
"Going forward, we are raising the age restriction for purchase of firearms and ammunition to 21 years of age."
The company, which previously had an age-limit of 18, said it had stopped selling "modern sporting rifles including the AR-15" in 2015 and now only sells handguns in Alaska.
It added: "Our heritage as a company has always been in serving sportsmen and hunters, and we will continue to do so in a responsible way."
Walmart's move comes after Dick's Sporting Goods, one of America's biggest sports retailers, said it would no longer sell firearms to people under 21 years old and pledged to stop selling assault-style rifles.
Florida gunman Nikolas Cruz had legally purchased a gun at a Dick's store, although it was not the weapon used in the massacre.
The 19-year-old former Stoneman Douglas student is accused of using an AR-15 assault-style weapon to carry out the killing.
Appearing on US television, Dick's chairman Ed Stack said: "When we saw what the kids were going through and the grief of the parents and the kids who were killed in Parkland, we felt we needed to do something."
The Florida massacre sparked a wave of youth-led protests and US officials are considering whether to pass stricter gun control measures.
The powerful National Rifle Association (NRA) traditionally opposes such curbs, citing the right to bear arms under the US Constitution's Second Amendment.
More from Florida School Shooting
Several major companies including airlines United and Delta and car hire firm Hertz have cut ties with the NRA amid public outrage over the Florida massacre.
US President Donald Trump says he has told NRA officials that "it's time" to strengthen US gun lawswhile also suggesting arming teachers to stop school shootings.