As Brenton Tarrant drove away from the New Zealand mosque where he allegedly went on a shooting spree, only 10 people were tuned into his live broadcast of the rampage on Facebook Live, according to archived versions of his page.

But the video, which shows dozens of people inside the Al Noor mosque in Christchurch being gunned down, has likely been viewed millions of times in various formats across the internet. The footage was recorded, repackaged and reposted on mainstream sites, fringe destinations with looser restrictions and in the web’s darkest corners only accessible with special software.

Facebook Inc. and Google’s YouTube were still working this weekend to keep the video off their own sites.

The vast cloning of the footage underlines a stark reality in the era of live online broadcasting: These videos can’t be cut off.

Artificial intelligence software isn’t powerful enough to fully detect violent content as it is being broadcast, according to researchers. And widely available software enables people to instantly record and create a copy of an online video. That means the footage now lives on people’s phones and computers, showing how little control the major tech platforms have over the fate of a video once it airs.