The Atonement is Incumbent Upon the One Who Ran Over a Victim
Question :
A woman had a two-year old son. He went out of the house into the road and was accidentally hit by a car belonging to one of his relatives. Is his mother obligated to do anything, bearing in mind that since this happened, she is suffering tremendously because of the accident?
Answer:
If the situation is as you have described in the question, then there is nothing incumbent upon the mother. The Diyah and atonement are only required from the person who ran over the child.
And we ask Allah to recompense the parents with goodness and to console them in their loss, and verily, we are Allah's and to Him shall we return.
Source:
Ibn Baz
Fatawa Islamiyah, Vol. 6 Page 180