A California Highway Patrol collision report says the 40-year-old Hart was a passenger in a 1970 Plymouth Barracuda that went off Mulholland Highway and rolled down an embankment around 12:45 a.m. Sunday.
The report says Hart and the driver, 28-year-old Jared Black, both suffered “major back injuries” and were taken to hospitals.
Another passenger, 31-year-old Rebecca Broxterman, only complained of pain.
The CHP report says the car immediately went out of control as it turned from a canyon road onto the highway.
The car was a gift Hart bought himself for his birthday in July, according to E! News.