Elon Musk will begin laying off Twitter employees on Friday morning, according to a memo sent to staff, as several Twitter employees file a class-action lawsuit claiming the layoffs violate labor law.

The email sent Thursday evening notified employees that they will receive a notice by 1:00 pm ET this Friday informing them of their employment status.

“If your employment is not affected, you will receive notification via your Twitter email,” said a copy of the email obtained by CNN . “If your employment is affected, you will receive a notification with next steps via your personal email.”

The email added that “to help ensure the security” of Twitter’s employees and systems, the company’s offices “will be temporarily closed and all badge access will be suspended.” The email concluded by acknowledging that it will be “an incredibly challenging experience” for the workforce.

The memo comes after news that Elon Musk was planning to lay off up to half of the company’s staff after acquiring it last week for $44 billion.

The class action filed on Thursday alleges that Twitter is violating the Federal Worker Adjustment and Retraining Notification Act after laying off some employees. The law requires an employer with more than 100 employees to provide 60 days written notice prior to a mass layoff “that affects 50 or more employees in a single workplace”.

“Elon Musk, the richest man in the world, has made it clear that he believes complying with federal labor laws is ‘trivial,'” attorney Shannon Liss-Riordan, who filed the suit, said in a statement to CNN . “We have filed this federal complaint to ensure that Twitter is held accountable under our laws and to prevent Twitter employees from unknowingly signing their rights.”

Twitter had around 7,500 employees before the Musk acquisition.

Musk began his tenure at Twitter by firing CEO Parag Agrawal and two other executives, according to two people familiar with the decision.

In less than a week since Musk acquired the company, his C-suite appears to have been almost entirely wiped out, through a mix of layoffs and layoffs. Musk also dissolved Twitter’s former board of directors.