From the California Highway Patrol:

On Tuesday, March 22, 2016, at approximately 6:00 PM, A 2001 GMC Yukon with three male occupants was traveling southbound on SR-271, approaching mile post marker 2.04, in Mendocino County. For reasons still under investigation, the Yukon briefly drifted off the west roadway edge. The driver over-corrected causing the Yukon to overturn multiple times. The driver and front passenger were ejected as the vehicle overturned. The driver sustained fatal injuries and was pronounced deceased at the scene. Both passengers suffered major injuries and were transported to Howard Memorial Hospital. Due to one of the passengers extensive injuries, he was flown to Santa Rosa to receive further care. The identity of the deceased is currently being withheld pending notification of next of kin. 

Agencies on scene were Cal Fire, Laytonville Ambulance, Veri-health, Leggett Volunteer Ambulance, Cal-Trans, and CHP.

The collision remains under investigation by the California Highway Patrol. It is believed that alcohol or drugs were a factor in the cause of this collision. 

Incident report here.