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.

Shares of Elon Musk’s electric vehicle maker are falling sharply Thursday as investors fear his dispute with Donald Trump could end up hurting the company.