You were doing great until you went stone-cold stupid with that comment.
Well, let's see. The guy had a history of domestic violence, drug charges, and weapons charges. We don't know why he still had access to a gun, but here are some of the things that may have prevented that from happening. Which of these would have met with NRA approval?
1. The court could have taken his gun away from him, provided that they knew he owned one, which they would have, if gun registration had been required.
2. If he had bought it from a private party, the sale would have not happened, if background checks would have been required for all gun purchases.
Or, he could have stolen the gun, which I doubt very much, since this apparently was an act of passion, which usually is done with whatever weapon is at hand.