Four of the seven Google employees who organized a 20,000-person walkout in November have resigned from the company, including two women who claimed Google retaliated against them for their internal activism. The latest to leave is Meredith Whittaker, who ran Google Open Research and has emerged in the past couple of years as a prominent voice demanding increased accountability from tech companies around uses of artificial intelligence.

In April, Whittaker claimed Google had retaliated against her for her role in the walkout and her advocacy work on AI ethics through AI Now, a research institute she cofounded that has received funding from Google. She had already been told her AI ethics work was no longer a fit for Google’s Cloud division. “It’s clear Google isn’t a place where I can continue this work,” Whittaker wrote in a farewell note posted on Medium, which urged employees to unionize, protect whistle-blowers, and insist on transparency around the technology they are building and how it will be used.

In the Medium post, Whittaker, who worked for the company for 13 years, said Google’s advantages in AI have propelled the company into new markets, like health care, fossil fuels, and city development. “The result is that Google, in the conventional pursuit of quarterly earnings, is gaining signi­ficant and largely unchecked power to impact our world,” Whittaker wrote. “I’m certain many in leadership—who learned what Google was and why it was great over a decade ago—don’t truly understand the direction in which Google is growing. Nor are they incentivized to.”

The employee resignations highlight growing hostility between Google and its most outspoken employees, who have grown increasingly organized and strident in their demands for significant changes to Google’s approach to issues including sexual harassment claims, military contracts, censored search in China, and equitable treatment of contract workers, who now outnumber full-time employees. That tension presents a challenge to Google’s open company culture, which encouraged employees to debate and dissent on internal forums, but established strong social norms around secrecy. Google evangelized this culture, elements of which have been adopted by other Silicon Valley firms, and the company’s response to employee activism is being closely watched.

Google says that Whittaker’s official role at the company was related to open source work and that Whittaker was repeatedly told she could continue working on AI ethics in her personal time.

In a statement, a Google spokesperson told WIRED, "Meredith Whittaker has decided to resign from her role in Google's open source program management team. Since 2016, Meredith has spent most of her time on work for NYU’s AI Now Institute and will leave the company to focus on this work. Google will continue to work with policymakers, aca­demics, the tech community and other leaders from across industries as we tackle these important issues, in addition to providing transparency into how we’re putting our AI principles into action."

Whittaker’s last day at Google was Monday, the same day another organizer, Celie O’Neil-Hart, the former global head of trust and transparency marketing at YouTube Ads, tweeted that she had begun a new job at Pinterest.

The walkout in November protested Google’s handling of sexual harassment claims, after The New York Times reported that Android founder Andy Rubin had received a $90 million exit package despite sexual misconduct claims. Nearly six months after the protest, Whittaker and fellow walkout organizer Claire Stapleton, a former marketing manager for YouTube who left the company in June, shared a message on Google’s internal mailing lists, claiming they faced retaliation from Google for organizing the walkout. Soon after, they hosted a retaliation town hall for employees to discuss concerns about an alleged pattern of Google punishing, sidelining, and pushing out employees who speak out.