Is the driver obligated to pay blood money (diyya) if he is surprised by a person who throws himself in front of his car, and despite his attempt to avoid collision, the accident causes the person's death?

The ruling regarding blood money (Diyyah) in car accidents is based on the principle: "That which cannot be avoided does not incur liability." Therefore, if the accident occurred without negligence on your brother's part (he adhered to the speed limit, took precautions, and used the horn), and it is proven that the fault lies with the fleeing person, then there is no liability or expiation (kaffarah) upon him.

However, if he could have avoided the accident but failed to do so, then this is considered accidental killing (qatl khata'), and two things are incumbent upon him: 1. Expiation (Kaffarah): Freeing a believing slave. If he cannot find one, then fasting for two consecutive months. 2. Blood Money (Diyyah): This is paid to the heirs of the deceased and is borne by the 'Aqilah (the relatives of the perpetrator from the father's side).

It is necessary to refer to the competent authorities to examine the circumstances of the accident and fully ascertain its details.