Tesla Incs shares slumped by nine per cent on Friday after CEO Elon Musk gave an emotional interview to the New York Times in which he told the newspaper he was preparing for several months of “extreme torture” from short selling investors.

Musk surprised industry analysts and worldwide markets last week when he Tweeted that he was considering taking Tesla private and had secured funding. The Securities and Exchange Commission (SEC) has reportedly already opened an inquiry related to his tweets, which initially sent Tesla stocks soaring, and may have contravened financial regulations.

Following the release of the interview, Tesla stock suffered its biggest daily slump in two years, with many on Wall Street questioning the ability of an increasingly erratic Musk to lead the electric car manufacturer. According to The New York Times, the firm is apparently looking for a number two who will be able to take pressure off of Musk, who has struggled with production issues for Teslas Model 3 sedan, a key release that has suggered a number of flaws.

“This past year has been the most difficult and painful year of my career. It was excrutiating,” said Musk in the interview. “Ive had friends come by who are really concerned.

Investors were also apparently worred by reports suggesting regulators were pressuring Teslas directors for details about how much information Musk has shared with them about his plans. According to Musk, he did not consult any of Teslas leadership team before his Tweet, and has no plans to relinquish his dual role of CEO and chairman. He also denies that board members complained to him about his activity on Twitter, despite two sources familiar with the matter claiming that many were angry they had not been briefed.

In the interview, Musk said he was preparing for “at least a few months of extreme torture from the short-sellers, who are desperately pushing a narrative that will possibly result in Teslas destruction.”