California Highway Patrol press release:

On June 20, 2015, at approximately 1705 hours, a 2007 Nissan Altima, driven by a 31 year old male of Redway, CA, was traveling southbound on US-101, just south of Myers Flat.  For reasons still under investigation, the Nissan made an unsafe turning movement to the right and traveled off the west roadway edge. The Nissan collided with a dirt embankment causing it to overturn multiple times.  The Nissan landed on its roof blocking the southbound #1 and #2 lanes. 

The driver of the Nissan suffered minor injuries as a result of the collision and declined medical attention on scene.  The right front passenger, a 32 year old female of Redway, CA, suffered fatal injuries as a result of the collision.  The four year old male juvenile suffered minor injuries as a result of the collision.  He was not transported and was released to the care of his father on scene.

The California Highway Patrol, Cal Fire, City Ambulance of Eureka, Meyers Flat Fire Department and Cal Trans all responded to the scene.  This collision remains under investigation by the Garberville CHP.

The female passenger that sustained fatal injuries appeared to not be properly restrained at the time of the collision.