The tweets are aimed at "shorts", or investors who borrowed shares of Tesla and immediately sold them with the hope that Tesla's share price would fall.
In one of the lawsuits, the plaintiff Kalman Isaacs said Musk's tweets were false and misleading, and together with Tesla's failure to correct them amounted to a "nuclear attack" created to "completely decimate" short-sellers.
"Am considering taking Tesla private at $420".
Tesla CEO Elon Musk used Twitter late Friday to taunt investors who have bet against his company, even though his previous Twitter comments have spurred a government investigation and shareholder lawsuits.
In a proposed class-action complaint filed with the federal court in San Francisco, Kalman Isaacs said the scheme was conducted in part to "completely decimate" short-sellers, eventually leading to an inquiry by the US Securities and Exchange Commission (SEC).
The two separate cases have been filed in a court in the Northern District of California, which is not far from where Tesla is located, Palo Alto. That would allow the shorts to buy back the stock at a lower price, return the shares to the lender, and pocket the difference.
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FILE PHOTO: Tesla Motors Inc Chief Executive Elon Musk pauses during a news conference in Tokyo September 8, 2014. Musk's tweet about taking Tesla private sent the stock soaring 11 percent Tuesday and cost short sellers roughly $1 billion, according to some estimates.
Musk has not offered evidence that he has lined up the necessary funding to take Tesla private, and the complaints did not offer proof to the contrary.
The complaint said the class period begins on the afternoon of August 7, when the defendants launched their "nuclear attack" on short-sellers, and ends the next day.
According to his complaint, Isaacs bought 3,000 Tesla shares on August 8 to cover his short position.
Isaacs accused Musk of making false and misleading statements to inflate Tesla's stock price, and that Tesla "doubled-down" on those statements by failing to correct them.