Another issue, if basing things on articles/news reports in media -of any form- is that not all shootings of any sort- make it into the news to begin with. In fact, most dont, unless it's a slow news day, or a child gets hit, or there's a race element (white/hisp. shooter vs. black shootee).
So it's a hard one to accurately document, short of accessing #s of GSV's in hospitals (which,l egally ,wont happen, due to Privacy Act, etc), police reports (not all police incidents make it onto the news either, unless the officer screws up royally -see NYPD, for recent examples) or some other means.
Some areas of some towns, for example, have so many shooting incidents on any given day, (be it defensive/offensive/accidental, whatever) that the news media dont even bother (and for that matter, even the cops dont bother, half the time..) unless, again, something really dramatic results from it. Excellent example- Springfield areas of Jacksonville. That area can average 6-12 shootings per any given day (even more on Welfare check days), yet folks in the rest of town would never even know or hear of it, if relying on news reports.