If the father went to the house to get the gun, and then back to the accident scene to shoot the driver, then that shows premeditation and malice of forethought, which would support a murder charge. By hiding the gun and not turning himself in immediately, he showed a consciousness of guilt, so that would rule out insanity.
Rather than tending to his wife and other two children, he engaged in revenge. That demonstrated a motive.
There's a good chance that he will be found guilty of murder.
If he is, there are legal limits, minimum and maximum, that set the range of his sentence. I doubt that a guilty verdict for murder can be sentenced with community service or probation.
Even if he is a member of a minority group, so were the victims and witnesses. Also, there's still the possibility that members of the jury and/or the judge will also be members of that same minority, if that reflects the demographics of the location.
As far as cultural mores, our courts are supposed to make judgments based on the statutes of the United States of America, the individual states, and the local jurisdiction. They are not supposed to be judging on tribal customs, sharia, the Talmud, the Bible, la cosa nostra, or anything else.
