If you are conscious you can refuse EMTs, regardless of severity of injury. You could be bleeding out and all your limbs chopped off, if you refuse they can't help you. They however will do their best to have you reconsider your decision. If you are unconscious they can help you as implied consent in the matter, where any reasonable person would consent. The police though would be able to stop the car from being driven, hah. Maybe police wasn't on scene yet? Weird story in any case