If you wanted to prevent NIU, all they had to do was put his name in the database.
Hardly, that would merely drive him to purchase the guns from an individual, rather than a licensed dealer. That might even be from an unlicensed dealer in stolen firearms. He wasn't far from the South Side of Chicago, where all handguns are illegal, and are freely available in back alleys and such, as are other sorts of "illegal" and legal but not for him, weapons.
Not true. He could still buy a firearm in another way.