The president of the Citizens Crime Commission of New York City pointed out the importance of lawful gun owners keeping their guns locked up, away from children and keeping ammunition separate from guns. Those 3 things would have prevented this tragedy. It sounds like the parents have much of the blame. I believe requiring tests and fees for gun ownership is a reasonable solution.
How tragic for the whole family. And now I'll read statements from people saying things like, "I was around guns all my life, and this didn't happen. It must be those video games."
I'd give the NRA just a little bit of a break if just once they responded to something like this with sincere sympathy, possibly with an offer of grief counseling for the family, and a suggested program to ensure it didn't happen again (other than restricting video games).