http://www.nationalgangcenter.gov/Su...-Gang-Problems
Compare with, http://www.fbi.gov/about-us/cjis/ucr...es/10tbl01.xls, you get a difference of <-10% change overall vs ~-2% in gang related homicides. That is just overall, would have to look more into it.
~9900 Firearm related homicides in 2011, 2020 gang related.