The shooter’s Twitter account, on which he posted content linked to white supremacist websites and photos of guns, was suspended around 2pm, more than an hour after the shooting.
However, segments of the video and gifs, uploaded by third parties, were still visible at the time of writing.
A Twitter spokesman said: “We are deeply saddened to hear of the shootings in Christchurch today. Twitter has rigorous processes and a dedicated team in place for managing exigent and emergency situations such as this.”
Facebook activated a crisis response for the shooting at 1:37pm, an hour after the attack.
In a statement, Facebook said: “Our hearts go out to the victims, their families and the community affected by this horrendous act.
“New Zealand Police alerted us to a video on Facebook shortly after the livestream commenced and we quickly removed both the shooter’s Facebook and Instagram accounts and the video. We’re also removing any praise or support for the crime and the shooter or shooters as soon as we’re aware.”
A Facebook spokesman said «as you can probably imagine, this is still an unfolding issue. We are still in the process of removing content from Facebook».
A YouTube spokesman said: “Our hearts go out to the victims of this terrible tragedy. Shocking, violent and graphic content has no place on our platforms, and is removed as soon as we become aware of it.”
The social media giants have come under increased global scrutiny in the past 24 months over their responsibilities in stopping hate speech and graphic content from being shared on their platforms.
In his manifesto, Tarrant wrote he developed his beliefs on the “the internet, of course. You will not find the truth anywhere else».
All three social media sites stated they would work with law enforcement.
A Spark spokesman said the company, Vodafone and New Zealand’s third-largest internet provider Vocus had agreed to block customers’ access to overseas websites that provided access to the video.
Many people have complained on social media about Australian TV broadcasters showing graphic footage from the video.
The Australia Media and Communications Authority reported that it received a «small number» of complaints about a «number of broadcasters» about the issue.
A Sky News spokeswoman said the broadcaster ran heavily edited footage that «did not show the shootings or the victims”.
A Network 10 spokeswoman said its new site 10 Daily «showed footage of the gunman walking towards the door of the mosque» but not from inside the mosque, and «warned about the nature of the vision in the accompanying story».
Channel Seven and Nine declined to comment.
New Zealand Police have urged social-media users not to share the footage.
Yan is a reporter for The Age.
Jennifer Duke is a media and telecommunications journalist for The Sydney Morning Herald and The Age.