As students at the Florida school where 17 people were recently killed returned to classes, a major gun retailer has announced it will stop selling the kind of weapon used in the attack.
Dick's Sporting Goods, which has more than 600 shops, said it would no longer sell assault-style rifles, and backed "common sense gun reform".
The move came as pupils and teachers made an emotional return to Marjory Stoneman Douglas High School.
Grief counsellors were on hand.
In the aftermath of the 14 February shooting, pressure has mounted on US politicians to act on gun control and for corporations to cut ties with the powerful National Rifle Association (NRA).
Firms including Hertz car rental, United airlines and Delta airlines have ended discounts to NRA members.
Dick's Sporting Goods announcement also came as Florida lawmakers proposed a package of gun control measures, including a controversial bill to arm school staff, including teachers.
"We have tremendous respect and admiration for the students organising and making their voices heard regarding gun violence in schools and elsewhere in our country," Dick's Sporting Goods said in a statement. "We have heard you. The nation has heard you."
The retailer said it was committing itself to:
- No longer selling assault-style rifles (The company had stopped selling such weapons after the 2012 Sandy Hook shooting but 35 shops run by a subsidiary had continued to do so.)
- Banning the sale of high-capacity magazines that allow more shots to be fired without reloading
- Not selling firearms to anyone under the age of 21
It said that while it supported the Second Amendment to the US Constitution, which protects the right to keep and bear arms, "gun violence is an epidemic that's taking the lives of too many people".
Dick's CEO Edward Stack told CNN he expected a backlash from some customers, saying "the hunt business is an important part of the business, no doubt about it".
The Parkland shooting suspect, 19-year-old Nikolas Cruz, bought a gun at Dick's but not the AR-15-style weapon he is alleged to have used in the attack, Mr Stack said.
"We did everything by the book, and we did everything that the law required, and he was still able to buy a gun," he told ABC.
Walmart, the largest seller of guns in the US, stopped selling high-powered rifles in its shops in 2015, citing low demand.
At Marjory Stoneman Douglas High School, a line of police officers, school staff and community members bearing flowers greeted some 3000 students who returned to classes on Wednesday morning.
"I'm not scared," 16-year-old Sean Cummings told the AFP news agency. "It's just weird to come back after everything that has happened."
But David Hogg, a senior student and now leading activist, said it was "just really hard to think about" what occurred two weeks ago.
"Imagine getting in a plane crash and having to get back on the same plane again and again and again and being expected to learn and act like nothing's wrong," he told NBC News.
The handling of the shooting by authorities sparked criticism after it emerged that the FBI and local police failed to follow up on multiple tips about Mr Cruz, and that an armed deputy at the school had stayed outside the school building while the attack took place.
Ernest Rospierski, a teacher at Marjory Stoneman Douglas, earlier told the BBC: "Usually, I always greet the kids at the door."
But this time he said he was going to tell them "how much it makes me legitimately excited to have them back in the room and to have the ability to be in front of them again".
The school's Building 12, the site of the shootings, will remain closed and cordoned off indefinitely.
There will only be a half day of classes, but the focus for students will be on reconnecting with friends and teachers, and sharing their feelings.
Armed school 'marshals'
Members of Florida's State House and Senate will soon begin reviewing proposed bills related to firearms, which need their approval and also that of Governor Rick Scott.
They would raise the legal age to buy rifles from 18 to 21 and giving police more control to seize weapons from mentally ill people.
A controversial $67m voluntary programme to arm school staff, including teachers, would ensure they were trained by law enforcement and allowed to carry concealed weapons on campus, according to the New York Times.
Lawmakers had already given an initial green light to what has become known as the "marshal programme", despite protests by many parents of Marjory Stoneman Douglas High School students.
They argued that educators should not have to take on the role of the police. A similar programme already exists in Polk County, in central Florida.
Governor Scott has previously said he opposes "arming teachers".
In addition to proposing a rise in the minimum legal age to buy all rifles, legislators from the budget committees from the Florida House and Senate want to impose a three-day waiting period for any gun purchases. Handgun buyers must already be at least 21 and wait for three days.
They also want to outlaw the sale of bump stocks - a piece of plastic or metal that allows semi-automatic rifles to fire dozens of rounds in seconds, like a machine-gun.
But a Democratic-backed amendment to ban assault-style rifles was rejected by the House Appropriations Committee.