Sheriff Dupnik allowed the shooter to obtain a gun.
Despite the fact that he was a known threat.
Even the local college banned him from campus.
Dupnik is responsible for a lot of crap, but he has no say whatsoever in who gets to own a gun in Pima County. Arizona uses the NICS database or a state-issued CCW permit to authorize gun sales.
Now, had the Pima County prosecutor not allowed the boy to skate on his drug charges 2 years ago, he might have been denied when the gun store did the NICS check. That might have changed things.