Sorry, I should be clear - I take issue instead with how you think restricting carry zones increases safety, for as far as I know it simply isn't relevant to mass shootings.
Well, placing strict regulations on how one attains a firearm is the first step whether it is through some combination of federal/state legislation and possibly even municipal. The next step is to make sure that those who are qualified to own a gun are in continuous safeguard of their firearm. We do this by restricting where they can actually carry them. There really is no point to carrying a firearm outside of a gun range, or designated hunting space. If anything having larger area's of carry leaves the gun owner to unnecessary risk involving theft/loss of the firearm. The loss/theft of a firearm is a very serious issue.