Does a person whose car (truck) ran over another person, after that person was hit by another car and pushed under his truck, leading to his death, have to fast for two months as expiation, knowing that he was not the direct cause of the collision and only learned of the incident later, and was the death caused by the first car or his truck?

If the driver did not exceed the speed limit or neglect any safety precautions, and knew that his car was in good condition allowing him to control it, then he is not liable for diyah (blood money) or kaffarah (definition) (expiation) for what occurred if he could not have avoided it. However, if he was negligent in safety precautions, he is held accountable for what his driving caused. If it is unknown which of the two drivers caused the person's death, and both were negligent, then the diyah is jointly incumbent upon their aqilah (male relatives responsible for paying blood money), and each of them must emancipate a believing slave or fast for two consecutive months. If the negligence was from only one of them, then he alone is responsible.