Enlarge / Tesla CEO Elon Musk in 2015. (credit: ODD ANDERSEN/AFP/Getty Images)

Tesla’s CEO roiled the stock market on Tuesday with a tweet suggesting that he might seek to take the company private at a price of $420—almost 20 percent above the company’s then-current price of around $355:

Am considering taking Tesla private at $420. Funding secured.

— Elon Musk (@elonmusk) August 7, 2018

Within minutes, the stock surged another $15 to $370 per share. The value has been swinging wildly ever since.

In a Twitter direct message to Ars Technica, Musk confirmed he was serious about the proposal. “Yes, might take Tesla private,” he said.