The 50-year-old Beverly Hills surgeon, whose patients included reality TV star Heidi Montag, musician Vince Neil and actor Lorenzo Lamas, was killed Aug. 16 on Pacific Coast Highway in Ventura County west of Malibu.
The Ventura County Star says the patrol's investigation concluded this week that Ryan died after making an unsafe turn, causing his southbound 1995 Jeep Wrangler to drift to the right and overturn down a rocky coastal embankment.
Ryan was trapped inside the vehicle with major head injuries.
Ryan was riding with his dog. The injured animal survived.