Elon Musk has sold at least $3.95 billion worth of Tesla shares since completing his $44 billion takeover of Twitter, according to new filings with the Securities and Exchange Commission Tuesday.

Context: Tesla's stock is down 52% so far this year. The electric vehicle company's market cap has fallen below $600 billion for the first time since June last year. 

• Musk's own net worth has dropped by $70 billion since he bid for Twitter in April.

The big picture: Musk has said publicly twice this year that he didn't plan to sell any more Tesla shares.

• The first time was last April when the Tesla CEO sold $8.5 billion of stock after he signed a deal to buy Twitter for $44 million.
• In August, Musk agreed with a Twitter user that he was "done selling" after offloading more than $6.9 billion in Tesla shares after attempting to withdraw from the agreement to buy Twitter ahead of the prospect of a legal battle that ended after he completed the takeover last month.
• "In the (hopefully unlikely) event that Twitter forces this deal to close *and* some equity partners don’t come through, it is important to avoid an emergency sale of Tesla stock," Musk tweeted at the time.

Worth noting: The National Highway Traffic Safety Administration reported Tuesday that Tesla informed the NHTSA on Nov. 1 that it's recalling just over 40,000 Model S and Model X vehicles due to a potential power-steering problem.

Between the lines: Investors are worried that Musk is too distracted by Twitter and is stretching himself and his Tesla team thin.

• Tesla is also facing growing competition from legacy automakers including GM and Ford while facing a slowdown in demand.

Editor's note: This article has been updated with new details throughout.