Two young Fort Bragg-area brothers died Tuesday evening after a crash of an all-terrain vehicle on the rural property where they lived.
Carter and Silas Wilson, ages 8 and 6, respectively, were riding together when the vehicle hit an embankment.
The CHP is investigating whether the boys were riding alone and how experienced a driver the older boy was. Mendocino Sheriff's Office detectives, meanwhile, still were conducting interviews to determine what happened.
The accident happened shortly after 7 p.m. on the property where the boys lived with their mother, Heather Perkins. Perkins' parents, Raymond and Karan Perkins, lived in a house on the same property.
The homes are off Highway 20 between Fort Bragg and Willits. The brothers had been wearing bicycle-style helmets but weren't using the vehicle's restraints.
The older boy had been driving across a grassy pasture when the ATV hit a dirt embankment, causing the vehicle to go into the air. It landed on its front end, throwing the younger boy to the ground.
The vehicle then continued on, throwing the older brother off, the CHP said.
Officers are not yet sure how fast the vehicle was traveling when it hit the embankment.
Six-year-old Silas died at the scene. Carter died at Mendocino Coast District Hospital.
The boys were Heather Perkins' only children, according to her sister, Jayme Johnson of Fort Bragg. The father does not live in Fort Bragg, she said.