Footage from an anti-Semitic attack in the German city of Halle was livestreamed overnight on Amazon's video gaming platform Twitch.
Two people were killed in the attacks on a synagogue and a kebab shop and one suspect has been arrested.
A spokesperson for Twitch said the video of the attack has been removed and the account it was posted from was suspended.
The company says it is "shocked and saddened by the tragedy that took place in Germany today, and our deepest condolences go out to all those affected".
New Zealand Prime Minister Jacinda Ardern said the Christchurch Call kicked into action after the video was livestreamed.
The Call is a partnership between governments and tech companies designed to eradicate extremism and terrorism online.
Ms Ardern said Amazon signed up to the Call following the 15 March Christchurch attacks and it has resulted in a prompt taking down of the footage.
"Amazon joined the Christchurch Call in New York, so the incident protocol that we've developed has kicked in.
"Companies are communicating as I understand with one other to ensure that that video does not spread online."
Ms Ardern said the second element, which involves technological development and research which is needed to stop livestreaming happening in the first place, is still a work in progress.
"We've all acknowledged that's work that is still ongoing but I think this demonstrates why it is so necessary and why that work must continue."
She said no-one underestimates the scale of the challenge to prevent such incidents happening in the future.
Two million monthly users, commentator says
Tech commentator Paul Brislen told Morning Report the Amazon platform is the default choice of gamers for streaming content.
"It has around two million users a month, so once something has been posted, it's relatively straightforward for someone else to grab it, make a copy, and share it with anyone on any other platform.
He said even with Amazon retroactively taking the stream down, it's too late.
"The horse has bolted. The internet doesn't share content, it copies content. Everytime someone makes a new version, you've got to start again from scratch.
"The trick is to stop it being streamed in the first place, but of course they make money from streaming video content so that's unlikely to happen outside government intervention."