My son was traveling at an appropriate highway speed when the truck in front of him stopped suddenly. He braked immediately and was able to slow down significantly, but not enough to avoid colliding with the back of the truck in front of him. He was going approximately 20 mph, still braking, when the collision occurred. His best recollection is that the vehicle's pre-collision system did not engage until after he collided with the truck. There was damage to the front end of the vehicle but it was not severe. My son moved the vehicle onto the shoulder of the highway and put it in park. The driver of the truck called the police. My sons got out of the vehicle. While they were talking with the other driver and the police, a fire started under the hood of the vehicle and within several minutes the entire vehicle was consumed. The wreckage was towed to 1022 Shannon Court, Livermore CA 94550. In July 2023 we were involved in an accident that impacted the front bumper, left front quarter panel, and Subaru EyeSight system of the same vehicle involved in this accident. Repairs after the July 2023 accident were performed by Kraft Body Shop in Santa Clara, CA. Repair and calibration of the Subaru EyeSight system were performed by Santa Cruz Subaru after that accident.