Gary Rooney had worked at Twitter for nearly a decade and was the director of "source to pay," a procurement role, in Twitter's European headquarters in Dublin when Elon Musk acquired the social-media platform for $44 billion in October 2022.

Musk sent a now infamous email to the workforce asking them to commit to an "extremely hardcore" work schedule or resign.

"This will mean working long hours at high intensity. Only exceptional performance will constitute a passing grade," the billionaire wrote in the email.

Anyone who didn't click yes on a link in the email to "be part of the new Twitter" by the next day would receive three months' severance, the message said.

Rooney did not respond to to the email and treated as if he resigned. Rather than leaving quietly, he brought a case to Ireland's Workplace Relations Commission, claiming unfair dismissal. He won and was awarded about $600,000.

Rooney told Twitter: "At no time have I indicated to Twitter that I am resigning my position," he replied a week later, according to the report. The company told him that not clicking yes was "treated as you having served notice to resign your employment."

The Workplace Relations Commission's report shows that on the day Rooney received Musk's email, he messaged a colleague on Slack, saying: "Hey — wanted to let you know im going. I need to step away for my own sake. I'm deeply troubled by whats going on here these days."

In another message, he wrote: "Iv made the decision not to press the yes button and wanted to drop in a goodbye here."

Twitter used these messages and others as evidence that he intended to leave the company. The commission found the Slack messages had "no relevance to the question as to what brought about the termination of the Complainant's employment."

Even though Rooney won his case, experts told Business Insider that it should serve as a reminder to all employees about the risks of using internal messaging systems.