Social networks struggled to cut massacre video

The social networks designed to spread messages at lightning speed struggled to harness ghastly images of a massacre in Christchurch, New Zealand, where at least one gunman killed dozens of worshippers during Friday prayer at two mosques.

In what Prime Minister Jacinda Ardern called a wellplanned terrorist attack, 49 people were killed and dozens injured in two shootings.

Portions of the horrific attack at one of the mosques had been broadcast live on Facebook by a man who police say also released a manifesto denouncing Muslims and immigrants.

The 17-minute video that included graphic footage of one of the shootings could be found on Facebook, YouTube, Twitter and Instagram more than an hour after being posted. While Facebook and Twitter took down pages thought to be linked to the gunman, the posted content was spread rapidly through other accounts.

Like previous episodes depicting graphic violence, disturbing images or misinformation around a national emergency, the social networks struggled to contain the gruesome content, which users said could be found easily after the original broadcast.

In order to evade detection, people appeared to be cropping the video or posting the text of the manifesto as an image — techniques used to evade automated systems that find and delete content.

Social media companies have heavily invested in those systems, with Facebook reporting last year that more than 99 percent of terrorism content by the Islamic State and al-Qaida was found and removed through artificial intelligence.

The New Zealand shooting highlights how social media companies continue to grapple with breaking news events, and raises questions about the effectiveness of their safeguards, which are designed to curb abusive content and incitements to violence.

The nature of live-streaming and of instantaneous amplification on the web also underscores the challenge of policing hateful content. Messages can spread globally in seconds while scrubbing them or restricting their reach can take much longer — minutes, hours or days.

“New Zealand Police alerted us to a video on Facebook shortly after the live-stream commenced and we quickly removed both the shooter’s Facebook and Instagram accounts and the video,” said Mia Garlick, a Facebook spokesman. “We’re also removing any praise or support for the crime and the shooter or shooters as soon as we’re aware. We will continue working directly with New Zealand Police as their response and investigation continues.”

YouTube said it had taken down thousands of videos related to the shooting, and asked users to help flag videos.

Reddit, in a statement, said that it was “actively monitoring the situation in Christchurch, New Zealand. Any content containing links to the video stream are being removed in accordance with our site-wide policy.”

Still, the tech companies were sharply criticized by Sen. Cory Booker, a Democratic candidate for president, who said Friday in New Hampshire that it was “unacceptable” for the companies to give “a platform to hate.”