More than two weeks after a terror attack in New Zealand was live streamed on Facebook, the social media company’s Chief Operating Officer Sheryl Sandberg said they were “exploring restrictions” on who can live stream video on the platform. Sandberg outlined the actions that the social media giant will take in the wake of the terror attack on two mosques in Christchurch that killed 50 people.

“The terrorist attacks in Christchurch were an act of pure evil,” Sandberg said in a letter published in The New Zealand Herald on Saturday. “All of us at Facebook stand with the victims, their families, the Muslim community, and all of New Zealand. It is deeply tragic when people face violence because of who they are and what they believe.”

Sandberg’s letter follows weeks of criticism in New Zealand over Facebook executives’ lack of response to the attack. Prime Minister Jacinda Ardern had called for a united global front against social media being used for violence. The attacker, a white supremacist, had live streamed the shooting on Facebook, videos of which went viral instantly.

Sandberg said Facebook has been working with the New Zealand Police to support their investigation. She said the attacker’s Facebook and Instagram accounts were taken down, and videos of the attack were removed.

“We have heard feedback that we must do more – and we agree,” she said. “In the wake of the terror attack, we are taking three steps: strengthening the rules for using Facebook Live, taking further steps to address hate on our platforms, and supporting the New Zealand community. First, we are exploring restrictions on who can go Live depending on factors such as prior Community Standard violations.”

Sandberg said the original video of the attack, which was shared Live, was re-shared and re-edited, making it harder for Facebook’s system to block it. “We are also investing in research to build better technology to quickly identify edited versions of violent videos and images and prevent people from re-sharing these versions.”

Sandberg said Facebook had identified 900 different videos showing portions of the attack.