"The New Zealand Police made us aware of a video on Facebook shortly after the live stream started, and both shooters were quickly removed Facebook and Instagram accounts and the video," said Mia Garlick, Facebook's policy director for Australia and New Zealand. in a statement.
Hours after the attack, however, copies of the cruel video continued to appear on Facebook, YouTube, and Twitter, raising new questions about companies' ability to manage malicious content on their platforms.
Facebook "removes any praise or support for the crime and shooters or shooters as soon as we understand it," Garlick said.
The New Zealand police called on social media users not to share the alleged footage and said they wanted to get it down.
CNN does not want this Post additional video information until more details become available.
Technology companies do not consider this as a priority.
Friday's video raises the question of how social media platforms handle offensive content. How soon should they be expected to remove him?
"While Google, YouTube, Facebook and Twitter all say that they are cooperating and acting in the best interests of citizens to remove this content, they are not actually because they keep you from revealing those videos," Lucinda said Creighton, senior adviser to the Counter Extremism Project, an international political organization.
Facebook's tools for artificial intelligence and human moderators were apparently not in the Able to discover the livestream of the shootout. The company said it was made aware of it by the New Zealand police.
"The tech companies do not see that as a priority, they're wrestling their hands, they say that's terrible," Creighton said. "But what they do not prevent this from reappearing."
John Battersby, an anti-terrorism expert at Massey University in New Zealand, said the country was spared massive terrorist attacks, in part because of its isolation. Social media had changed that.
"This comrade streamed the shootings live and his backers cheered him on, and most of them are not in New Zealand," he said. "Unfortunately, once online, it can be downloaded (online)," he added.
The spread of the video could inspire copycats, said CNN lawyer Steve Moore, a retired special agent for the FBI.
"What I would say to the public is this: Would you like to help terrorists, because if you do, you are sharing this video exactly as you are doing," Moore said.
"Do not share or be part of the video," he added.
Hadas Gold, Donie O & Sullivan, Samuel Burke and Paul Murphy contributed to this report.