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Snowdrops are in bloom this weekend as Dunblane shakes off its winter chill and looks ahead to spring.

But in this Scottish town, the carpet of while petals marks not just a new season but also the anniversary of a school shooting that led to an immediate change in gun laws.

Twenty years ago this Sunday, a local gun owner walked into the town’s elementary school and fatally shot 16 first-graders and their teacher before killing himself.

Pictures of anguished parents running through the streets for news of their children deepened public outrage, and a crusade to tighten controls — led by townspeople and victims’ families — won widespread support.

The "Snowdrop Campaign," which took its name from the only spring flower in bloom at the time of the massacre, resulted in a ban on all private hand-guns.

That response contrasts with the inertia surrounding efforts to tighten gun controls in the United States, where public opinion remains much more divided on whether such changes are necessary.

It puzzles some of the Dunblane families, for whom shootings such as the 2012 Sandy Hook massacre in Connecticut bring back painful memories.

A memorial to the children of Dunblane. Keir Simmons / NBC News

“You feel how they feel and we got something done about it, whereas for families in America there is still suffering,” said Alison Ross, 20, whose older sister was among the victims and whose mother Pam helped organize the Snowdrop Campaign.

“You understand their want for something to be done because that is how we felt as well,” she told NBC’s U.K. partner, ITV News. “Something had to change, and it did change.”

Mick North, whose daughter Sophie was killed in the March 13, 1996 massacre, believes the changes made Britain a safer place.

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Related: South Carolina Democrats Love Their Guns — and Back Some Controls

“School and college shootings occur with sickening regularity in the U.S., yet too many politicians claim that everything but gun ownership is responsible,” he told the Radio Times this week. “Their blinkered and uncritical support of gun rights means that the problem will never go away.”

He said parallels have been drawn between the shootings at Dunblane and Sandy Hook — but there's a critical difference.

"The horror at the mass killing of children and teachers, the sympathy for their families, were the same as we’d experienced. The legacy was not,” he said.

In 2015 the U.S. saw more mass shootings — defined as incidents in which four or more victims are shot — than days in the calendar year. Yet there is almost no demand for curbs on gun ownership such as the one imposed in Britain after Dunblane.

Instead, President Obama is ordering tighter enforcement of federal laws so that anyone selling firearms — at stores, at gun shows, over the Internet — must get a federal firearms dealer’s license and check the backgrounds of all buyers.

Obama's initiative also calls for hiring hundreds of examiners to help the FBI do the increased background checks — roughly 22.2 million were conducted in 2015 — and it requires weapons merchants to notify the Bureau of Alcohol, Tobacco, Firearms and Explosives if their guns are lost or stolen.

Even these modest changes have encountered strong opposition, most notably from the National Rifle Association which said in January that none of the changes would have prevented any of the shooting tragedies that Obama cited at a tearful news conference unveiling the initiative.

“The timing of this announcement, in the eighth and final year of his presidency, demonstrates not only political exploitation but a fundamental lack of seriousness,” the NRA said.

It is true that Britain’s handgun ban failed to prevent another mass shooting. In 2010, a taxi driver shot dead 12 people in a killing spree in Cumbria, northwest England. It later emerged that the driver held a valid shotgun certificate as well as a longstanding firearms license for pest control and clay pigeon shooting.

20 years on - a tribute to Dunblane. Today's front page #scotpapers pic.twitter.com/IZiiGidcaJ — The Daily Record (@Daily_Record) March 12, 2016

Overall, firearm offences involving any type of injury have declined since the 1996 handgun ban, falling to 1,340 last year compared to more than 5,000 only a decade ago. There were 19 deaths from crimes involving guns in 2014-15, the lowest recorded figure in a quarter of a century, according to the Home Office, whose figures cover England and Wales. However, outlawed handguns accounted for 11 of those 19 deaths.

The majority of police in England and Wales are unarmed — reflecting lower levels of violence aimed at police officers — and officers discharged their guns just twice in 2015 out of more than 14,000 firearms operations. And the most common weapon used in violent crime in Britain is not a gun, but a knife.

The Dunblane shooter, unemployed 43-year-old Thomas Hamilton, was the legal owner of all four handguns used in the attack: two Browning pistols and two Smith & Wesson revolvers.

However, the police firearms-licensing office was unaware that complaints had been made about Hamilton's behavior towards young boys at after-school clubs that he ran.

Parents gathered outside the elementary school in Dunblane, Scotland, after the shooting on March 13, 1996. Louis Flood / AP, file

The Snowdrop Campaign successfully argued for deeper background checks of firearm certificate applicants.

Only weeks after Dunblane's 1996 tragedy, a similar mass shooting shook Australia when 35 people were killed at the site of a historic penal colony at Port Arthur, Tasmania.

The shooter, who was later assessed to have the IQ of an 11-year-old, told investigators that he'd paid cash for firearms at a local gun dealer.

Australia’s government outlawed automatic and semi-automatic rifles, in addition to pump-action shotguns, while a nationwide buyback scheme also saw more than 640,000 weapons turned in to authorities.

Today, Dunblane's population of 8,000 still reflects on the massacre that cast a shadow over an entire generation.

It's the 20th anniversary of Dunblane this week. Someone local must have planted these snowdrops today. Nice touch. pic.twitter.com/WqKmvL0EVA — David McArdle (@davemcardle) March 5, 2016

Among the young children who escaped from Dunblane Primary School was Andy Murray, now 28 and a British tennis champion. His mother, Judy, revealed she had once given a ride to the shooter, who was involved in local boys' after-school clubs.

“He was a bit of an odd bod, but I wouldn’t have thought he was dangerous,” she told the Daily Telegraph in 2014. “He’d been in my car.”

She added: “I had friends who had lost children, so I went to the funerals. It was impossible to believe something like that could happen in your little town. Sometimes it still is.”