The Connecticut policeman mentions an interesting detail. Apparently, Lanza replaced the magazine of his rifle every time, before entering another room, even if the magazine in the rifle was not empty yet. The policeman suggested that he had learned this trick by playing first person shooters. While this would be difficult to prove, it sounds plausible. Playing FPSs may not have made Lanza a killer, but might have made him a somewhat more effective one.
That said, while I do not condone gratuitous violence in video games (or other entertainment media for that) I do not believe censure would do any good (news media covering this kind of events probably are much more harmful); I also believe that more effective controls over the acquisition and possession of firearms would be appropriate, regardless of these tragic events (the existing rules are way too easy to circumvent), but I do not really believe this would stop a determined psychopath.
While we are at this, I also believe better mental health services should be put in place, also regardless of these events, nevertheless I expect most mass shooters would just "fly under the radar" (I can not find it right now, but someone pointed out that, according to current criteria, most of the mass shooters involved in recent episodes would *not* qualify for compulsory psychiatric treatment *before* they went on a killing spree.)
So... does anything work? Can we "fix" this just by changing some rules? I would say no. Rules cannot fill in for the loss of moral values.
As another poster mentioned, this is society eating itself. Sometimes I really wonder whether it is still redeemable.