United Kingdom, July 5 -- Caitlyn Jenner is "numb with shock" over the shock death of her longtime friend and manager Sophia Hutchins.

Sophia, 29, is believed to have collided with a car while riding an all-terrain vehicle on a road close to Caitlyn's property in Malibu, California last week, before the ATV plummeted into a ravine.

A source told RadarOnline.com: "Caitlyn is numb with shock. She is absolutely devastated and can't believe what's happened. Sophia was a big part of her life."

TMZ previously reported that emergency services were called, but Sophia was pronounced dead at the scene. No one else is believed to have been injured in the accident.

Sophia took over managing Caitlyn's career in 2017 following the reality star's di...