Tesla investors tapped the breaks on Friday, pushing shares of the electric car maker down 8.9 percent after unsettling comments by founder Elon Musk were reported.

Musk, in a revealing interview, said he has been working up to 120 hours a week and needs Ambien to fall asleep at night.

In the interview, Musk, alternating between laughter and tears, told the New York Times the struggle over the last year to get production of the Model 3 going at full speed was “excruciating.”

“This past year has been the most difficult and painful year of my career,” he said.

Investors must have gotten unnerved.

Tesla shares closed Friday at $305.50, down 7.8 percent — leaving them down 4.7 percent for the year and 20 percent from their close on Aug. 7 when Musk first tweeted about taking the company private.

The company is the subject of a widening probe by the Securities and Exchange Commission. Regulators are looking into statements the company made regarding its production-plagued Model 3 and the tweet Musk made earlier this month about having “funding secured” to take the company private at $420 a share.

The Tesla board also briefly sought out a strong No. 2 to Musk — but has given up on that endeavor, according to the Times report.