Tesla announced several promotions, including a replacement for O'Brien, in a blog post on Friday, but did not name a new chief accounting officer.
Elon Musk smoked dagga and drank whisky in a live interview conducted by comedian Joe Rogan on Thursday.
Overall, Morton appears to have parted ways with Tesla amicably, stating that he still believes in the company's overall mission, as well as its future prospects.
A month later, Musk was the centre of attention again when he tweeted that he had secured enough funding to take his electric-car company Tesla private for $420 per share. He took one drag from what Rogan described as a joint containing tobacco mixed with marijuana, which is legal in California. "I don't actually notice any effect".More news: Elon Musk puffs on marijuana joint during live interview
The 47-year-old billionaire later said he wasn't a "regular smoker" of marijuana because he doesn't find it "very good for productivity". The Securities and Exchange Commission reportedly served Tesla with a subpoena on August 15 about Musk's intentions. They have fallen about 18% since Musk's tweet on taking the company private on 7 August.
Mr Musk has said the company is producing more than 5,000 Model 3 electric cars per week, and cash generated from the sales will bring sustained quarterly profits.
"We have been calling for a co-CEO or COO to assist to codifying the leadership structure and in so doing, the culture at Tesla", said James Albertine, analyst at brokerage Consumer Edge, speaking before the promotions were announced.
Shares of Tesla fell more than 6 per cent to reach a five-month low on Friday morning following the departure of the company's chief accounting officer, Dave Morton, who resigned less than a month into the job on Friday.More news: Here’s What Shahid Kapoor Has Named His Son
"We think this is further evidence that the time is now for management and the board to address these issues".
The announcement sent Tesla stock surging by more than 10 percent. Tesla's stock plunged, then extended declines after Gabrielle Toledano, the head of human resources who's been on a leave of absence, told Bloomberg News that she won't rejoin the company.
Viecha also restated Tesla's forecast that it will build 50,000 to 55,000 of its Model 3 sedans in the current quarter, and indicated the company's working capital will improve as production increases, Spak wrote.More news: Mourinho jokes over cost of Man United sacking him