Tesla Chief Executive Officer Elon Musk has reportedly sold 4.4 million shares of the electric vehicle maker worth $3.99 billion, US securities filings showed on Thursday, in sales likely to help finance his planned purchase of Twitter.

In a tweet, Elon Musk said in a tweet that there are “no further TSLA sales planned after today.”

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On Thursday, Tesla lost ground amid investor concerns that Musk may have to sell Tesla shares to fund his $21 billion equity contribution to his $44 billion buyout of Twitter Inc.

Musk uses his Twitter account to make business announcements and promote his enterprises.

He muses about technology and trade, but has also posted jokes about women’s breasts and once compared Canada’s prime minister to Hitler. He regularly weighs in on global events, as he did in March 2020 when he tweeted that “The coronavirus pandemic is dumb.”

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Recently, Musk used Twitter to criticise one of the platform’s top executives and an attorney, in one case in a reply to a far-right activist who promoted the discredited conspiracy theory that pizza parlours around the US were being used to traffic children.

Musk’s tweets were followed by a wave of harassment by other accounts that targeted both individuals. For Vijaya Gadde, an 11-year Twitter employee who heads up the company’s legal, policy and trust divisions, the harassment included racist and misogynistic attacks, in addition to calls for Musk to fire her.

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Musk has long used the megaphone of his Twitter account to punch back at critics or people he opposes, such as when he attacked a diver working to rescue boys trapped in a cave in Thailand by calling him a “pedo,” short for paedophile. The diver had previously mocked Musk’s proposal to use a sub to rescue the boys. Musk, who won a defamation suit filed by the diver, later said he never intended “pedo” to be interpreted as “paedophile.”

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Musk’s use of Twitter has also led to problems for his own companies. In one August 2018 tweet, for instance, Musk asserted that he had the funding to take Tesla private for $420 a share, although a court has ruled that it wasn’t true. That led to an SEC investigation that Musk is still fighting.

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More recently, Musk appeared to have violated SEC rules that required him to disclose that he’d acquired a 5% stake in Twitter; instead he waited until he had more than 9%. Experts say these issues aren’t likely to affect his Twitter acquisition.

Last year another federal agency, the National Labour Relations Board, ordered Musk to delete a tweet that officials said illegally threatened to cut stock options for Tesla employees who joined the United Auto Workers union.