My concern with this is, of course if there are more guns there are more gun deaths. But how does that impact overall violent crime and murder rates? If the same number of people die with or without guns in the same place... it's just an incomplete look at the overall picture.
For example, in Oregon, WA, and California, when gun laws were increased it didn't reduce violent crime or murder rates. Or even gun crime, as far as that goes. They have all gone up.
Also, most of the cities and states with higher gun crime rates (not to mention higher overall violent crime and murder rates) have terrible access to mental healthcare compared to others... which likely has a pretty big impact as well.