Yep. You have a vehicle with tires and brakes which were designed for the standard size vehicle, being expected to work for a vehicle with 2-3 times the weight.
18 people at 150 pounds is over 3,000 pounds, that’s hard to stop if the car was going 60+mph at the bottom of the hill. Driver was said to be not from thee, so it’s either he didn’t know thee was a stop sign or the brakes totally failed.