5 Mass Shootings That Shaped Gun Laws

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Written By: J. Lasswell
February 23, 2023

From Polytechnique to Christchurch: Exploring Mass Shootings That Impacted Gun Control

There is no argument at the forefront of school security more catalytic than that of gun control. Whether it’s about children having easy access to guns, troubled potential perpetrators being able to buy a gun, or simply the firing rate of certain rifles, the surrounding argument is explicitly polarizing. Here in the US, gun ownership is a protected right - and to some, a fundamental tenant of their American identity. Meanwhile, many Americans are questioning whether protecting this right is worth living under the constant fear of gun violence. 

We don’t wish to use our platform to state any political opinions, as we recognize that participating in an incredibly politicized fight doesn’t forward our mission to bring all schools to a baseline of competent safety and security. Rather, we find identifying the threshold of violence that different countries can endure before regulating guns could yield a more productive discussion. Whether you see gun regulation as a sacrifice that private citizens have to make in the name of security, or you see it as a convenient opportunity for the government to regulate their inhabitants, one thing cannot be denied: no instrument has instigated more change in the contemporary world than the modern-day rifle.

Listed below are five events that have most directly influenced change in gun-ownership laws in their respective countries along with information about the perpetrators, revealing the motivations that would bring them to kill en masse

These events are listed chronologically - 


In the scope of violence in learning institutions, no event was more clearly motivated by deep misogyny than the massacre at École Polytechnique massacre in Montreal in 1989 (rivaled perhaps only by the perpetrator of the 2014 Isla Vista killings). The perpetrator, ML, ironically was raised by a mother that fought to protect him from an abusive father and worked hard to keep them out of poverty. It’s believed his misogyny was motivated by an abusive relationship with his sister, along with his own insecurity regarding his unmet expectations while women were beginning to be included in his chosen field of learning. After purchasing a Ruger Mini-14, a lightweight semiautomatic rifle, ML would scope the Polytechnique campus seven times before committing an attack on the school which would take the lives of 14 women and wound another 10. 

Just a few days following the event, a petition was written by two professors from École Polytechnique, urging the Canadian government to implement stricter gun control measures which garnered over 500,000 signatures. This led to the passage of two bills popularly known as the Firearms Act of 1995. This new regulation mandated the training of gun owners, screening of firearm applicants, a waiting period of 28 days for new applicants, rules on gun and ammunition storage, registration of all firearms, restrictions on magazine capacity for semi-automatics, and restrictions on certain firearms.

To learn more about the Polytechnique massacre, listen to this in-depth Tomorrow's Problem Podcast episode.

An even more recent impact to Canadian gun legislation: the 2020 attacks in Portapique, Nova Scotia. After a string of attacks and arsons were committed by a gunman with an AR-style rifle, Canadian PM, Justin Trudeau announced a complete ban on "assault-style" firearms. This ban would receive international attention, as Canada’s neighbors to the southern border did, and continue to quarrel with the idea of banning certain firearms, with AR-style guns at the forefront of the conversation.


While the UK isn’t known for high-profile school shootings, the events at Dunblane Primary School in Dunblane, Scotland, in 1996 account for some of the most gut-wrenching violence ever to befall school children. The perpetrator, TH already had a troubled history within his community stemming from complaints that he had taken inappropriate photographs of young boys (amongst other inappropriate behaviors) while being a leader in the UK Scout Association. It’s believed TH perceived his label as a pariah and subsequent failure as a business owner is what caused him to react violently towards his community. 

TH would retaliate against his community by entering Dunblane Primary School in Dunblane, Scotland with four legally-owned handguns and killing 16 young students and a teacher while injuring 15 others. To this day, it remains the deadliest mass shooting in UK history. 

The Conservative government under Prime Minister John Major enacted the Firearms Act of 1997, which prohibited all cartridge ammunition handguns, except for .22 caliber rimfire, throughout England, Scotland, and Wales. After the next election, the Labour government, led by Prime Minister Tony Blair, introduced the Firearms (No. 2) Act of 1997 which outlawed the remaining .22 cartridge handguns.

Port Arthur 

What makes the Port Arthur massacre in 1996 such a significant event isn’t simply the magnitude of the losses - 35 dead and 24 injured makes it one of the worst mass shootings in the southern hemisphere - what is most notable about this event is how fundamentally it changed gun ownership in Australia, as well as the nation’s overall attitude toward guns.

The perpetrator, MB, was motivated to initiate this attack by perceived wrongdoing stemming from Seascape, a bed & breakfast owned by victims David and Noelene Martin, which perpetrator MB believed was stolen from his late father. However, the attack was amplified by MB’s deeply-engrained psychopathy, which caused him to extend his violence to anyone that was in eye view. MB started his rampage by murdering the owners at Seascape, then committed an attack on close by tourist attractions with a Colt AR-15, before being caught trying to commit suicide by setting Seascape on fire with himself inside. 

After the attack, Australia's Prime Minister, John Howard, established gun control regulations, firearm buyback programs, and devised the National Firearms Agreement. This prohibited civilians from owning semi-automatic rifles, semi-automatic shotguns, and pump-action shotguns, while also implementing consistent firearm licensing standards.


While it’s impossible to issue a warning for upsetting content without piquing the interest of the more morbid reader, let it be known that this deeply-distressing event lacks the benefit of a palatable conclusion. In 2011, 69 children were emotionlessly hunted down and killed on Utøya, an island off the coast of Norway by a far-right terrorist, AB, as a means to impose fear on the families of his political opposition. Another eight people were killed in this campaign by a bomb in a different location. This highly prolific shooting is juxtaposed by its nation’s idyllic disposition and already restrictive firearm allowances, which then only allowed gun ownership for hunting or sport shooting. 

AB's motivations for the attack were rooted in his extreme far-right ideology, which he detailed in a 1,500-page manifesto. In this tediously lengthy document, AB expressed his opposition to multiculturalism, Islam, and what he saw as the erosion of traditional European values. The island of Utøya was hosting its annual Norwegian Labour Party AUF Youth Camp, where hundreds of the children of his political opposition were attending, making them ideal targets in the eyes of AB. Unlike his counterparts on this list, AB surrendered to the police and is living in relative comfort in the Norwegian Correctional Service.

While it took a decade to rally political support, the Norwegian parliament was able to pass a law in 2021 banning the Ruger Mini-14 rifle model that was used in the massacre and other semi-auto rifles for hunting.


Proceeding the incident that took 51 lives in a rampage in two separate mosques in 2019, the response of the New Zealand government was an immediate ban on assault rifles, drawing praise and criticism from all over the world. However, based on this horrific procession of leisurely violence, all live-streamed from the shooter’s POV, it would be unseemly to judge the reaction of a sparsely-populated country that underwent such a violent attack. 

The shooter, BT, had expressed interest in white ethnonationalism and had been donating to various far-right identity organizations for the previous decade. BT was a gun enthusiast who owned shotguns, rifles, and the gun that would become a symbol of the future controversy: the AR-15. After writing a manifesto condemning modern-day immigration practices, BT planned and shot and killed 51 Islamic worshippers and wounded 40 at two separate mosques, only 3 miles apart.

Three weeks later, New Zealand’s Parliament voted almost unanimously to introduce a nationwide ban on semi-automatic weapons and assault rifles. The NZ government also set up commissions with the purpose of understanding the issues surrounding dangerous ideologies, the role of social media, and access to weapons.

Whether it’s an ideology that requires violence, the envy of unmet expectations, or retaliating from public embarrassment, the trend that ties all these events together is misperceived wrongdoings. Each of these perpetrators found it necessary to take up arms against their existential enemy, and by doing so further confounded their objective by treating innocent individuals as casualties of war. Unfortunately for these killers, the world is populated predominantly by innocent individuals, and violence - gun violence - doesn’t have a place in a world that grows more fatigued every day from this overdue issue. Furthermore, these actions tend to provide momentum for their opposing ideology to enact change, generally by restricting gun ownership rights in their respective countries. 

Perhaps this aggression is a remnant of an archaic way of thinking, perhaps it’s an inclination that certain individuals lacking logic or restraint can’t overcome. However, we see that when these behaviors are unearthed, many countries have no reservations about limiting the rights of their people rather than confronting this national agony again. Can you blame them?