HOUSTON, US

Hundreds of Twitter employees resigned Thursday ahead of Elon Musk's 5 p.m. ET deadline in which the social media company's new CEO demanded an "extremely hardcore" cultural reset with more work and longer hours.

"And just like that, after 12 years, I have left Twitter," tweeted Satanjeev Banerjee.

Musk purged Twitter's 7,500-person staff by nearly half just two weeks ago after taking over the company in a $44 billion buyout, with many more employees resigning shortly thereafter.

Twitter had about 2,900 workers remaining before Musk sent out an e-mail Wednesday demanding an overhauled work ethic for those wanting to stay with the platform, similar to the billionaire's expectations at his other companies, Tesla and SpaceX.

“Going forward, to build a breakthrough Twitter 2.0 and succeed in an increasingly competitive world, we will need to be extremely hardcore,” Musk wrote. “This will mean working long hours at high intensity. Only exceptional performance will constitute a passing grade.”

After the deadline hit, what one employee called a "mass exodus" began, with hundreds of workers posting farewell messages and salute emojis on the Slack instant messaging platform announcing they had said "no" to Musk’s ultimatum.

“I’m not pressing the button,” one departing employee posted, according to The Verge technology news website. “My watch ends with Twitter 1.0. I do not wish to be part of Twitter 2.0.”

“It feels like all the people who made this place incredible are leaving,” messaged another Twitter staffer. “It will be extremely hard for Twitter to recover from here, no matter how hardcore the people who remain try to be.”

Employees deciding to leave Twitter have been told they will receive a severance package of at least three months’ pay.

Workers who decide to stay do not know how Musk plans to compensate them with stock options now that Twitter is a private company. However, Musk has said that “exceptional” performers will receive stock like they do at SpaceX, which is also a privately-held firm.

The New York Times reported that Musk and his team met with some Twitter workers who had not checked "yes" to his new expectations before Thursday's deadline, trying to stop “critical” employees from leaving.

“We look forward to working with you on Twitter’s exciting future,” said a company e-mail sent to workers late Thursday which was obtained by CNN.

Musk also appeared to scale back his demand that all employees return to the office for at least 40 hours a week, but that did not appear to sway many to stay.

“I have worked here at Twitter for over 11 years,” one employee wrote on Slack. “Back in July, I was the 27th most tenured employee at the company. Now I’m the 15th."

"Where did all these chopped onions come from?” messaged another employee.

Twitter has already started recruiting outside engineers to see if they want to join “Twitter 2.0 - an Elon company,” according to The Verge.