Had the gun laws we have now been able to work, a few of those guys would have been declined the purchase of the firearm. Certainly the two Virginia guys would have been denied. The system is broke. The laws we do have don't work. The exchanging of guns between two private entities must be made illegal. Guns need to be registered so that we know where they are and who owns them and who is handing them to whom. If your AR-15 is registered to you, and you sell it to your buddy, you'd have to register that sale. If that gun is used in a crime and not registered, you should be on the hook.
That will push those to look to the black market for guns. But that is currently not needed. Making the guns harder to get would deter half of these lone wolf nut jobs. Making them resort to knives and bombs would also be a deterrent since knives are more personal and making a bomb is a bit scary.
The facts are that we do have gun controls. Those gun controls need to be enforced. We then should all move to ban extended magazines and make the sale of guns from individual to individual a much more formal process.
Those three steps would likely have saved lives. Perhaps the black market for guns becomes more accessible in the future with these steps, but we'll tackle that problem when we get to it.
These are suburban kids going to a local gun store to buy guns legally with the intent of using them in a commision of a crime. These are not gang bangers buying hot guns out of the back of a van in the ghetto.
It's past time for change. No one is coming for anyone's guns. We must make it harder for these maniacs from obtaining them.