The Facebook exec who helped hunt down Russia’s political ads is leaving the company

Alex Stamos, Facebook’s chief security officer and one of the key execs who helped the company track down Russian political ads on the service, plans to leave the company, according to a source familiar with his role.

Update: Stamos tweeted Monday afternoon that he is “still fully engaged with my work at Facebook,” though did not say that he was staying at the company indefinitely. He also confirmed that his role internally has changed. “I’m currently spending more time exploring emerging security risks and working on election security.” Our sources say that while Stamos is still at Facebook, he does plan to leave. The New York Times reported that he plans to stay at Facebook until August.

Stamos, who joined the social giant almost three years ago after a very public stint in a similar role at Yahoo, ran the team inside Facebook tasked with hunting down ads related to the Kremlin’s efforts to sow unrest in the U.S. ahead of the presidential election.

But Stamos’s responsibilities have eroded over the past few months, and most of his team was reassigned to other managers inside the company, including Chris Cox’s product group, according to two sources familiar with his role.

Stamos also lost his day-to-day role overseeing Facebook’s security team back in December, and didn’t always see eye to eye with Facebook COO Sheryl Sandberg about how the company should handle the aftermath of the 2016 presidential election, the New York Times reported Monday. The Times was first to report Stamos’s departure.

More recently, Stamos, who was one of Facebook’s most vocal executives on Twitter, tweeted a thread over the weekend defending the company for its role in the recent Cambridge Analytica scandal before abruptly deleting the tweets. Stamos said he, “should have done a better job weighing in.”

This isn’t the first time that Stamos has left a job seemingly at odds with his bosses. His decision to leave Yahoo in 2014 was at least partly to do with disagreements he had with CEO Marissa Mayer over the company’s security standards, which he felt were not strict enough.

Stamos is the most high-profile Facebook executive to leave since the 2016 election, and really the first public indication that Facebook’s leadership team might not be on the same page about how to deal with the company’s fake news problem. Facebook has a very tight and long-tenured executive team, and while Stamos was not necessarily in CEO Mark Zuckerberg’s most immediate circle, he had a significant role at a very significant moment for the company.

This article originally appeared on Recode.net.