I don't know the family situation, or the kid's prior behavior, so don't have basis to criticize. I will say, that unless dad had been out shooting with his son (to at least observe handling practices, attitude about wielding a deadly instrument), he shouldn't have given a gun as a gift - not even if the kid is/was a model citizen.
The parents are going to have to relocate.
he could not have legally bought a gun, he would have to lie about his psych drug prescription.
Gun laws work, but they can not get around the idiot factor.