Then the problem is the person, not the easy access to weapons
Yes and no. The problem is the person but they will pass all the tests - no criminal record, no history of mental illness, stable member of society, etc. etc. etc. So the only control you have is is the access to the weapon. You either ban he weapon, or you prevent the person having direct control of access to the weapon.
As to why gun shop owners and the police don't cause problems I can make two suggestions;
- Do they have direct access to the weapons after they leave work
- What percentage of the population are they and what percentage of the problem do they cause