. . .but black-on-black homicide has nearly doubled, and the victims/perpetrators are getting younger. Firearms are the most common death weapon.
I suspect that there are many elements at work here, but what I'd like to point out is that the main age group in question isn't old enough to buy, own, or sell a firearm. That would indicate what gun owners have said all along: that firearms used in criminal misuse are obtained illegally, not in gun stores or at gun shows.