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.

Wall Street's stock indexes ended lower on Thursday in choppy trade as a slump in Tesla shares offset news of progress in tariff talks between U.S. President Donald Trump and Chinese leader Xi Jinping.

Investors fear that the dispute between Elon Musk and President Donald Trump "will stop their friendship and change the regulatory environment for Tesla on the autonomous front over the coming years under the Trump administration,