The man killed Friday when the all-terrain vehicle he was driving flipped near Paso Robles was identified as Jacob Hoagland Raines, 34, of Morro Bay.
CHP officials said Raines was traveling southbound on the Dubost Winery property on Chimney Rock Road about 7:15 p.m. Friday when the ATV began to fish-tail and rolled over.
One other passenger, a 29-year-old Los Osos woman, suffered major injuries and was taken to Twin Cities Community Hospital in Templeton. The other two passengers suffered minor injuries.
Raines was traveling at an excessive speed when the crash occurred, and none of the four occupants were wearing seatbelts or helmets, according to the CHP.
Alcohol was believed to be a factor in the crash, which remained under investigation Friday, according to the CHP.