Elon Musk

pushed back on criticism from one of Tesla’s most vocal supporters amid growing concern about the billionaire CEO’s ability to manage Twitter and his other businesses.

• What happened? Ross Gerber, CEO of Gerber Kawasaki Wealth Management and longtime investor, tweeted about a perceived lack of leadership at the electric vehicle maker and said it’s "time for a shakeup." Musk replied by asking Gerber for his "great ideas" for Tesla and its board, and telling him to go "back and read your old Securities Analysis 101 textbook."

• Why it matters: The discord comes as Tesla’s stock is down more than 60% since the start of the year. Meanwhile, Musk has sold nearly $40 billion worth of Tesla stock in the past year, with much of that going to fund his purchase of Twitter — despite repeatedly saying he would stop selling down his stake.