According to police, the teen's car, now at an impound lot, swerved into oncoming traffic on West King's Highway, and slammed head-on into a trash truck.
The driver of the car, 18-year-old Zachary McGehrin, remains hospitalized.
His two passengers, 17-year-old Victoria Garvin, and 18-year-old John Sherman Jr., died at the scene. Sherman is the cousin of the West Caln Police Chief who responded to the crash.
Chief Curt Martinez said he only discovered his cousin was among the victims once they pulled ID from his pocket.
The cause of the accident remains under investigation, but the driver of the trash truck says the car never slowed down. He escaped without injury.