LOS ANGELES—A Tesla involved in a fatal crash on a Southern California freeway last week may have been operating on Autopilot before the wreck, according to the California Highway Patrol. 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 was killed when his Tesla Model 3 struck an overturned semi on a freeway about 2:30 a.m. The driver’s name has not yet been made public. Another man was seriously injured when the electric vehicle hit him as he was helping the semi’s driver out of the wreck. The CHP announced Thursday that its preliminary investigation had determined that the Tesla’s partially automated driving system called Autopilot “was engaged” prior to the crash. …