"[Richard Nielsen] had nothing in his background that would have issued any red flags or they would have pulled…[his application] when he applied," said Sgt Jerry Brewster to WBTV 3 in regards to the murder-suicide who purchased the gun only an hour before the act.
You've read too much Philip K Dick or watched too many Spielberg movies if you think background checks can predict future crimes. They're only intended to stop known criminals, mentally unstable citizens, and illegal immigrants from legally purchasing a firearm, nothing more. All those people are still capable of purchasing knives and non-projectile weapons and hazardous chemicals.
I'm not saying this means the system needs to be revamped or enlarged to cover these obvious gaping holes. I'm just saying that background checks aren't an end-all solution.
Personally (and this will not make me many friends) I'm not an advocate on increasing gun and weapon control. If someone wants to commit a crime, they're not going to let a little thing like the illegal possession of a weapon to stop them; it's just one more charge on the rap sheet. Gun and weapon control does two things: it makes acquiring a weapon for a repeat offender more difficult (but not impossible), and it makes it more difficult for an innocent and healthy citizen to acquire the means to protect themselves.
Background checks, while I agree they are a necessary bureaucratic evil, they aren't intended to fix the problem. Only rehabilitation programs can do that.