Copies of the footage reviewed by Reuters showed that some users had recorded the video playing on their own phones or computers to create a new version with a digital fingerprint different from the original. Many shooting games allow players to toggle between close-range and long-range weapons, and the gunman switched from a shotgun to a rifle during the video, reloading as he moved around.
Facebook, Twitter, Alphabet Inc and other social media companies have previously acknowledged the challenges they face policing content on their platforms.More news: Christchurch residents pay tribute to victims
Joshua Buxbaum, chief executive of Irvine, California-based moderation technology company WebPurify, said Facebook and other services could employ image recognition or other types of AI to identify copies in additional ways.
If Facebook wanted to monitor every livestream to prevent disturbing content from making it out in the first place, "they would have to hire millions of people", something it's not willing to do, said Vaidhyanathan, who teaches media studies at the University of Virginia.
"The stream is not analysed, stored or processed by LIVE4 in any way, we have no ability (even if we wanted to) to look at the live streams as they are happening or after it's completed", he said in written comments to Reuters. Earlier past year, YouTube star Logan Paul posted a clip of a dead body hanging from a tree in Japan, prompting the Google-owned video portal to remove his channels from a preferred advertising program. Police said a fourth person was arrested Friday but that was "not related to these events".
He said the company condemned "the actions of these awful persons and their disgusting use of our app for these purposes".More news: Hero charged attacker during New Zealand mosque massacre, says witness
"Our hearts are broken over today's bad tragedy in New Zealand", YouTube, which is operated by Google, said in a Twitter posting. "We will do whatever is humanly possible for it to never happen again".
A spokesman for New Zealand's interior ministry said the video is likely to be classified as objectionable content under local law and could be illegal to share.
"We are also removing any praise or support for the crime and the shooter or shooters as soon as we are aware", it added. "Groups have deliberately spread it and those accounts should be closed down".
Portions of the video were also spreading by individuals on Twitter, which said it, too, was working to remove the content and had suspended the shooter's account.More news: Tokyo court acquits Mt Gox CEO of major charges
Experts said the companies could set their detection tools and removal processes to be more aggressive, but YouTube and Facebook have said they want to be careful not to remove sensitive videos that either come from news organizations or have news value. "Take some ownership. Enough is enough".