• One of the managers of Google Brain, Samy Bengio, announced Tuesday he's leaving the company.
• It's the highest-ranking team member to leave the company amid the fallout of well-known artificial intelligence researcher's departure from Google.
• Google Brain is an AI research team at Google.

Samy Bengio, a well-known researcher at Google's research group Brain, announced on Tuesday he's resigning from Google.

Bengio is the highest-ranked official to depart amid the fallout from Google's handling of ethics researcher Timnit Gebru, a well-known artificial intelligence researcher at Google who said the company abruptly fired her last fall after she requested clarity about a retracted paper.

"This is one of the most difficult emails I can think of sending to all of you: I have decided to leave Google in order to pursue other exciting opportunities," Bengio wrote in an email to his Google research team obtained by CNBC. "There's no doubt that leaving this wonderful team is really difficult." His last day is April 28.

Bengio oversaw Gebru's team and said in December that he wasn't notified the company had fired Gebru. He started at Google in 2007, according to his LinkedIn profile.

Bloomberg first reported Bengio's resignation.

"I stand by you, Timnit," he wrote in a Facebook post in December. "I also stand by the rest of my team who, like me, was stunned and is trying to make sense of all this. In particular the Ethical AI team, but also the broader Brain Research team."

Gebru was the technical co-lead of the Ethical AI Team at Google and worked on algorithmic bias and data mining. She's a well-known advocate for diversity in technology and is the co-founder of a community of black researchers called Black in AI.

CEO Sundar Pichai vowed to investigate after industry-wide outrage at Gebru's firing. In February, the company said it concluded the investigation and made tweaks to diversity and research policies. It declined to share investigation findings.

But that didn't stop the fallout. The company fired Margaret Mitchell, Gebru's co-lead, in February, alleging she transferred electronic files out of the company. Academics turned down funding from Google. At least a few employees have resigned, citing the company's handling of Gebru's research and departure.

Though Bengio didn't mention Gebru specifically in his departure email Tuesday, he gave kudos to his team for improving their "understanding of machine learning and its impact on the world."

"I've learned so much with all of you, in terms of machine learning research of course, but also on how difficult yet important it is to organize a large team of researchers as to promote long term ambitious research, exploration, rigor and diversity and inclusion."

Neither Google nor Samy Bengio immediately responded to requests for comment.

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