What must a young man do to ease his conscience after he hit a girl with his car when he was sixteen years old, and did not tell his parents about it, and does not know the girl's fate?

If the driver was not exceeding the speed limit and the child suddenly crossed the road and collided with the car without any negligence on the driver's part, then he is not liable, and nothing is incumbent upon him. The driver is absolved of responsibility if the accident was due to an act of God (force majeure), or due to the action of the injured party himself, or due to the fault of another. However, if the driver was negligent or remiss, he must ascertain the impact of the accident (injury or death), and the ruling will be determined accordingly. If he is unable to do so, the case should be referred to the Sharia courts or the competent authorities.