Though at least two Google engineers had earlier resigned to protest the dismissal of artificial intelligence (AI) researcher Timnit Gebru, Bengio is the highest-profile employee to go.

Bengio spent about 14 years at the company and was among its first employees involved in a decade-old project known as Google Brain that advanced algorithms crucial to the functioning of various modern AI systems.

Andrew Ng, an early Brain member who now runs software startup Landing AI, said Bengio “has been instrumental to moving forward AI technology and ethics”. Another founding member, Jeff Dean, now oversees Google’s thousands of researchers.

Google Brain researcher Sara Hooker in a tweet described Bengio’s departure as “a huge loss for Google”.

Bengio said he decided to leave Google to pursue “other exciting opportunities” and that his last day would be April 28.

It all started when Google fired fellow researcher Gebru in December after she threatened to quit rather than retract a paper.  Gebru has said the company wanted to suppress her criticism of its products and its efforts to increase workforce diversity. Google has said it accepted her offer to resign.

However, it then fired staff scientist Margaret Mitchell in February, claiming she transferred electronic files out of the company.

Mitchell has said she tried to raise concerns about race and gender inequity and speak up about Google’s problematic firing of Dr. Gebru.

Bengio had defended the pair, who co-led a team of about a dozen people researching ethical issues related to AI software. In December, Bengio wrote on Facebook that he was stunned that Gebru, whom he was managing, was removed from the company without him being consulted.

Though he did not mention the firings in his farewell note, they influenced his decision to resign, people familiar with the matter said, speaking on condition of anonymity.

Bengio wrote in the email: “I 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 so as to promote long term ambitious research, exploration, rigor, diversity and inclusion.”