New Zealand has never been the perfect country you might imagine from afar, from the quirky stories about lovelorn gannets and avocado heists, but it is generally safe, and stable, apart from the earthquakes. In these times, that makes it an idyll. It is telling that three days ago, the greatest threat in the island nation – the headline news – was an outbreak of measles.

Then, in a matter of hours on Friday, 49 people were shot dead in attacks on two mosques in Christchurch, the largest city in the South Island, their deaths livestreamed on Facebook. Explosive devices were found attached to cars, and the city was put on lockdown. There was no creeping threat, no public debate: New Zealand’s terror-risk level went from a perceived zero to an unequivocal high.

It is, as my friend from Christchurch messaged me this morning, “inconceivable”. There are many words for this horror, but that is the one I and many others can’t get past. There is no terrorism in New Zealand, I’d have told you before I went to bed on Thursday night – and wondered why on earth you’d asked. Growing up there, I had the kind of idealised childhood my parents had in Britain in the 1950s. One reason my parents decided to move from Dorset, when my sister and I were young, was to recapture a way of life that seemed to have been lost elsewhere, where not only did you know your neighbours’ names, they’d stop by unannounced – that took some getting used to – and make it abundantly clear that their door was always open.

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Even in the age of Islamic State, New Zealand remained entirely untouched. The 1990 Aramoana massacre, in which 13 people were killed by one man followed a dispute between neighbours.

In recent years, the biggest threat in New Zealand has been the land itself. The last, great tragedy in our nation’s history – and it is comparable only in the scale of the crisis – also happened in Christchurch: the 2011 earthquake, in which 185 people died. (Two people also died in the 2016 Kaikoura earthquake.) The country banded together for the recovery effort in a way that reinforced our sense of national identity: hardworking, collegial, enterprising, fair.

That cannot be the case here. The “Kiwi way” on which we New Zealanders pride ourselves – mostly classless, happily multicultural, egalitarian, welcoming – has been challenged, and in the most devastating way possible. Like any imagined collectiveness, it was only ever partially true. It was certainly sometimes invoked complacently or defensively by pakeha (white) New Zealanders, to protect the somewhat imaginary identity we hold dear. Earlier this week, I saw a tweet from a fellow New Zealander, following news that a politician had been assaulted on his way to work: “New Zealand, no. We don’t do this.” Well, we do.

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Our politics is mostly centrist, our government more stable, our discourse less openly toxic than is becoming the global norm, and for that we know we are hugely lucky. But the result is that we feel removed from (certainly geographically), and maybe even above, those forces for violence, hatred and division. They are certainly increasingly on show in our closest neighbour, Australia (where the Christchurch suspect is a citizen) – but that almost serves to bolster our national complacency.

With our founding treaty with the indigenous Māori people, our national anthem half-sung in te reo (“the language”), and our ethnically diverse cities, New Zealanders can feel pretty good about our multicultural society. Even the film-maker Taika Waititi’s statement that “New Zealand is racist as fuck” sparked a heated nationwide debate, the general tenor of the counterargument being: “We’re not racist like Australia.”

But the truth is, before Christchurch became the earthquake city, it was known as the skinhead city – the least multicultural of New Zealand’s three largest conurbations, 84% white at the last census compared with 74% for the country as a whole, with a steady, insidious white supremacist presence. There have been protests against Asian immigration since 2004. They are the city’s second-largest ethnic group but only make up 9.4% of the population. In 2010 a Korean backpacker was murdered. As a sociologist said of Christchurch the year after, following a racist campaign by a group called the Right Wing Resistance: “There’s a bit of a tradition of white supremacy.”

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Islamophobia is not mainstream in New Zealand the way it is in Australia or the UK. The national Middle Eastern population is so nominal as to be grouped with its Latin American and African populations: a total 1%, though there is high immigration from Malaysia, Indonesia and other predominantly Muslim countries in Asia. But in the internet age, those strains of hatred that previously we “New Zealand Europeans” might have once felt free to dismiss as “a South Island thing” are being bolstered. Nowhere is an island any more. As a nation, we have perhaps been slow to wake up to that. Today we did so in the most horrific way possible.

“It feels eerily not real,” wrote my sister from the other side of the world this morning. “Like it can’t be happening here.” There is a 1981 song, by the New Zealand band Blam Blam Blam, called There Is No Depression in New Zealand. Sometimes referred to as “the alternative national anthem”, it is a biting satire of unemployment, industrial strife and anti-apartheid protests over the Springboks rugby team’s tour that year – the irony being, of course, that there are very high rates of depression in New Zealand. There is no terrorism in New Zealand, until there was, and now it has changed for ever.

• Elle Hunt grew up in New Zealand. She is a commissioning editor for Guardian G2

• Crisis support services can be reached 24 hours a day. In New Zealand, the crisis support service Lifeline can be reached on 0800 543 354. In Australia, Lifeline is 13 11 14. In the UK and Irish Republic, contact Samaritans on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. Other international helplines can be found at www.befrienders.org.