NEW YORK (AP) —  Tesla CEO Elon Musk’s surprising proposal to take the electric car maker private has prompted regulators to suspend trading in the company’s stock.

The unusual step taken early Tuesday afternoon came shortly after Musk dropped a bombshell on his Twitter account by announcing he had lined up the financing to buy all of Tesla’s stock at $420 per share. That would cost about $70 billion, making it one of the biggest buyouts in U.S. history.

The disclosure initially raised questions whether the eccentric Musk was joking, but he then amplified on his plan in a subsequent tweet that said he intended to create a special fund that would allow all current Tesla shareholders to retain a stake in the car maker if they want.

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