Shootings at two Christchurch, New Zealand, mosques on Friday have reignited debate over social media’s handling of violent and extremist content.

A Facebook account bearing the same name as the alleged gunman apparently livestreamed the massacre on Facebook, and a manifesto was posted on a Twitter account by the same name as well.

The Twitter account, which violated the platform’s policies, has since been suspended and the site is working on taking down any existing video content related to the violence.

In a statement to HuffPost, a Twitter spokesperson said the company is “deeply saddened by the shootings,” noting that it has procedures for addressing such content.

“Twitter has rigorous processes and a dedicated team in place for managing exigent and emergency situations such as this,” the spokesperson added. “We also cooperate with law enforcement to facilitate their investigations as required.”

Facebook New Zealand spokesperson Mia Garlick told HuffPost the company was alerted by police to the livestream on its site, and “quickly removed the shooter’s Facebook and Instagram accounts and the video.”

The platform also pledged to delete any sympathetic messages to the attacker or attackers as it becomes aware of such content. It remains unclear exactly how many perpetrators were involved.

“Since the attack happened, teams from across Facebook have been working around the clock to respond to reports and block content, proactively identify content which violates our standards and to support first responders and law enforcement,” Garlick added. “We are adding each video we to find to an internal data base which enables us to detect and automatically remove copies of the videos when uploaded again.”

Facebook urges users to report any content violations so that the videos can be blocked on its platform.

According to CNN, Facebook’s human moderators and its artificial intelligence were unable to detect the launch of the livestream.

On Twitter, YouTube stated that it is “working vigilantly to remove any violent footage” on its platform, indicating that the content had spread rapidly online and suggesting social media companies are finding it challenging to rein in.