Caitlyn Jenner‘s longtime friend and manager, Sophia Hutchins, is dead following a tragic ATV accident near Caitlyn’s home … TMZ has learned.

Sophia was pronounced dead Wednesday morning in Malibu, according to law enforcement and family sources. We’re told Sophia was riding the ATV on the road where Caitlyn lives when she struck the bumper of a moving car — that impact forced the ATV over the shoulder … sending it, and Sophia, plummeting 350 feet down into a ravine.

Our sources say the first responders who reached Sophia, pronounced her dead on the scene. Two people in the car Sophia struck were not injured. It’s unclear if Caitlyn was home at the time, or if she witnessed the fatal collision. We do know no one else was harmed on the ATV.

In addition to their longtime friendship, Hutchins also worked as Jenner’s manager, overseeing business ventures and public engagements.

Sophia was 29.