Maybe if the dad kept the weapon away from his disturbed teenaged son and actually paid attention to him, this wouldn't have happened.
No, I don't think more useless laws are going to help. Even when we do have laws that are supposed to keep guns out of the hands of disturbed individuals, the systems often don't "talk" to each other and people fall through the cracks, like Cho, the Virginia Tech mass murderer. Others acquire their weapons illegally, like the Columbine killers. Or steal them from others in the household, like Adam Lanza, who was terribly failed by society and his family when it was quite clear that he was extremely disturbed and needed institutionalization. Nothing will change because people don't care and don't pay attention to even members of their own household.