(Mendocino, CA) -- A sixth Hart family member is confirmed dead after their SUV plunged off a Northern California cliff. Mendocino County authorities have announced that a body found in the surf ten days ago near the crash site is that of twelve-year-old Sierra Hart. Two of her siblings are still missing and presumed dead. Investigators believe that Jennifer Hart intentionally drove off a cliff last month with a blood-alcohol level over the legal limit. Others in the vehicle may have been drugged with a Benadryl-type medicine. Sierra's autopsy and toxicology reports are pending. The Washington family left its Woodland home in a hurry and drove through Oregon on its way to the rocky California coastline.