LOS ANGELES—The driver of a Tesla involved in a fatal crash that California highway authorities said may have been on operating on Autopilot posted social media videos of himself riding in the vehicle without his hands on the wheel or foot on the pedal. The May 5 crash in Fontana, a city 50 miles east of Los Angeles, is also under investigation by the National Highway Traffic Safety Administration. The probe is the 29th case involving a Tesla that the federal agency has probed. In the Fontana crash, a 35-year-old man identified as Steven Michael Hendrickson was killed when his Tesla Model 3 struck an overturned semi on a freeway about 2:30 a.m. Hendrickson was member of the Southern California chapter of a Tesla club who posted numerous photos and video on social media of his white Model 3. One video on his Instagram account showed him riding in the …