Kevin Systrom, Instagram’s former CEO, and Mike Krieger, its chief technology officer, said on Friday that they would step down because they were reportedly upset over Facebook management increasingly steering Instagram’s strategy.

Previously, Mosseri was leader of Facebook’s news feed tool, before moving to Instagram in May to become its vice president of product.

“Since we announced our departure, many people have asked us what we hope for the future of Instagram,” Systrom and Krieger wrote in a joint statement. “To us, the most important thing is keeping our community — all of you — front and center in all that Instagram does. We believe that Adam will hold true to these values and that Instagram will continue to thrive.”

Mosseri’s title will be head of Instagram rather than CEO as Systrom had been. Facebook did not say why it changed the title.

Mosseri takes the job at a pivotal moment for Facebook, which is undergoing slowing growth. Technology analysts consider Instagram to be one of Facebook’s hottest properties, and a key source of potential revenue and user growth for the company.

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While Facebook’s reputation has been damaged in recent months due to data privacy mishaps like the the Cambridge Analytica scandal and failing to prevent the spread of misinformation during the 2016 U.S. presidential campaign, Instagram has generally avoided controversy.

On Friday, Facebook said it had suffered a major hack that resulted in up to 50 million accounts being potentially compromised. Facebook executives said the hack could have potentially affected Instagram, as well as other third-party apps people may have connected with their Facebook account to log in.

Facebook said Monday that some of Mosseri’s immediate duties would be to recruit a new executive team, including includes engineering, product, and operations leaders.