By Vibhuti Sharma and Arjun Panchadar

(Reuters) - Tesla Inc Chief Executive Elon Musk was filmed smoking marijuana and wielding a sword on a webcast, just hours before the automaker said its recently-appointed accounting chief would leave, the latest in a string of unusual behavior and executive departures that have stunned investors.

Shares of the electric carmaker tumbled more than 6 percent on Friday to $263.24, with investors on edge after a tumultuous August during which Musk proposed and then abruptly pulled the plug on a go-private deal.

Chief Accounting Officer Dave Morton resigned after just one month in the job because of discomfort with the attention on the company and pace of work during that time, Tesla said in a filing on Friday. It later said that Chief People Officer Gaby Toledano would not return from a leave of absence, just over a year after joining.

Later on Friday, Tesla named a new president of automotive operations, promoting eight-year Tesla employee and former Daimler truck exec Jerome Guillen into the role overseeing all automotive operations and reporting to Musk.

That move, described in a company blog with several other promotions as a result of board and management discussions, gives Musk a seasoned auto industry veteran to lean on at a time when some investors have called for a new chief operating officer. Shares barely moved after hours, when the promotions were announced.

Morton and Toledano, whose departures come shortly after the U.S. Securities and Exchange Commission opened an inquiry into Musk's aborted privatization plan, join dozens of senior executives who have left Tesla.

"Since I joined Tesla on August 6th, the level of public attention placed on the company, as well as the pace within the company, have exceeded my expectations. As a result, this caused me to reconsider my future," Morton said in the filing.

Late on Thursday, Musk was filmed drinking whiskey, briefly smoking marijuana and wielding a Samurai sword during a 2-1/2-hour live Web show with comedian Joe Rogan that swiftly spread across social media.

Taking a puff from a joint, which Rogan said was a blend of tobacco and marijuana and legal in California, Musk said he "almost never" smoked.

"I'm not a regular smoker of weed," Musk said. "I don't actually notice any effect ... I don't find that it is very good for productivity."

It was the latest in a string of unconventional behavior by the billionaire South African native who is also CEO of rocket startup SpaceX.

Even before Musk's surprise Aug. 7 tweet that he had funding "secured" for a go-private deal, Tesla had been under scrutiny from investors, analysts and short-sellers as it works to hit production targets and slow its cash burn.