“It’s spreading like a virus,” Ms. Hochul said, demanding that social media executives assess their policies to ensure “everything is done to make sure this information doesn’t spread.”

There may be no easy answers. Platforms like Facebook, Twitch and Twitter have made progress in recent years, experts said, in removing violent content and videos faster. Following the shooting in New Zealand, social platforms and countries around the world joined an initiative called Christchurch Call to Action and agreed to work closely together to counter terrorism and violent extremism content. One tool that social sites have used is a shared database of hashes, or digital fingerprints of images, which can flag inappropriate content and remove it quickly.

But in this case, Ms. Douek said, Facebook appeared to have failed despite the hash system. Facebook posts linked to the video posted on Streamable generated more than 43,000 interactions, according to CrowdTangle, a web analytics tool, and some posts lasted more than nine hours.

When users tried to flag content as violating Facebook’s rules, which don’t allow content that ‘glorifies violence’, they were in some cases told the links weren’t against the policies. of Facebook, according to screenshots seen by The New York Times.

Facebook has since begun removing posts containing links to the video, and a Facebook spokesperson said the posts violated the platform’s rules. Asked why some users were told that posts linking to the video did not violate its standards, the spokesperson did not get an answer.

Twitter had failed to remove many posts containing links to the filming video, and in several cases the video had been uploaded directly to the platform. A company spokeswoman initially said the site might remove some instances of the video or add a sensitive content warning, then later said Twitter would remove all videos related to the attack after The Times asked. clarification.

A spokeswoman for Hopin, Streamable’s proprietary video conferencing service, said the platform was working to remove the video and remove the accounts of people who uploaded it.