A Google software engineer who wrote and circulated a petition against the companys potential bid on a contract with Customs and Border Protection said Monday that shed been fired.

I was just informed by Google that I am being terminated, Rebecca Rivers wrote on Twitter.

Rivers was placed on leave earlier this month along with another employee, Laurence Berland, who protested against hate speech on YouTube, prompting roughly 200 employees to walk out of the companys San Francisco offices in support of the two. Google said the two employees had been placed on leave for violating the companys policies regarding access to sensitive documents and monitoring employee calendars, but protest organizers said the companys treatment of the pair amounted to retaliation. Bloomberg reported Google sent a company-wide email Monday announcing that four employees in total had been fired for data security violations that day.

Rivers efforts follow increasing tension between Alphabet management and employees over the companys work with the Department of Defense, its handling of sexual harassment allegations, and alleged retaliation against critical employees. Google reportedly hired a law firm known for its union-busting tactics last week, a move presidential candidate Bernie Sanders called unacceptable. The company has also reportedly limited employees opportunity to pose questions to management, a former staple of its famously open culture, and advised employees against having raging political debates in online company forums or in person.

Rivers did not immediately respond to a request for comment on the reported firing.

Outraged employees in the group Google Walkout for Real Change wrote in a Medium post that the social network recently implemented a policy of document secrecy and classification with the ulterior motive of justifying targeted firings and preventing unionization.

Using this policy, Google did all it could to frame our colleagues as leakers. This is a lie, they said.

Meredith Whittaker, an artificial intelligence researcher who left Google earlier this year after leading global employee protests of more than 20,000, wrote on Twitter, It’s happened. Google is illegally firing organizers. This is craven retaliation, and I ask everyone who can to show up and support.