For months, Tesla shareholders were tormented by Elon Musk’s role in the administration of President Donald Trump. But any relief brought by his formal government exit last week quickly turned to fear as the electric-vehicle maker’s chief executive traded barbs with his former boss.

Shares of Tesla dropped by 14.2% as the market closed Thursday, the electric vehicle company’s 11th-worst day on the market ever. At one point in Thursday’s back-and-forth, Trump threatened the federal contracts that funnel billions toward Musk’s companies.

As Elon Musk and Donald Trump take jabs at each other online, their respective businesses are plummeting in value.