Prime Minister Jacinda Ardern has disclosed publicly for the first time that she inadvertently watched the video footage of the Christchurch terror attack.
In preparing the way for next week's international anti-terrorism tech summit in Paris, she has highlighted the "staggering reach" of the alleged mass murderer's live-stream video of the shootings - even to her own eyes.
"I use and manage my social media just like anyone else. I know the reach of this video was vast, because I too inadvertently saw it," the Prime Minister says in an op-ed article published this weekend in the New York Times.
"Many people report seeing it autoplay on their social media feeds and not realising what it was - after all, how could something so heinous be so available?"
Ardern and the President of France, Emmanuel Macron, will co-chair the summit of world leaders and tech industry chiefs with the aim of securing pledges to implement the "Christchurch Call" to prevent online posting of terrorist content, to ensure its rapid removal, and to prevent use of live-streaming as a tool to broadcast terrorist attacks.
She said the March 15 attack on two Christchurch mosques, which left 51 dead and dozens of others with bullet wounds, used live-streaming as a weapon to spread a hateful vision.
The Paris summit on Wednesday will be held alongside the "Tech for Humanity" meeting of G7 digital ministers, of which France is the chair, and France's separate "Tech for Good" summit. Ardern will also meet civil society leaders on Tuesday to discuss the content of the Christchurch Call.
Explaining the extraordinary reach of the Christchurch terror video, she said the original live-stream, just short of 17 minutes, was viewed some 4000 times before being removed from Facebook. Within the first 24 hours, 1.5 million copies of the video had been taken down from Facebook. There was one upload to YouTube every second in the first 24 hours.
"This attack was part of a horrifying new trend that seems to be spreading around the world: It was designed to be broadcast on the internet."
The footage was banned by New Zealand's chief censor four days after the shootings, on pain of a fine of up to $10,000 or up to 14 years in jail for sharing the clip, defined as "objectionable" material.
Ardern acknowledged potential difficulties in achieving the Christchurch Call, but said none of those involved in the Paris summit wanted digital platforms used for terrorism.
"Numerous world leaders have committed to going to Paris, and the tech industry says it is open to working more closely with us on this issue — and I hope they do. This is not about undermining or limiting freedom of speech. It is about these companies and how they operate.
"I use Facebook, Instagram and occasionally Twitter. There's no denying the power they have and the value they can provide."
She said social media connected people and the bid to prevent harm must not compromise "the integral pillar of society that is freedom of expression".
"But that right does not include the freedom to broadcast mass murder."