pdq, your figure may not be accurate.

"The total number of gang homicides reported by respondents in the NYGS sample averaged nearly 2,000 annually from 2006 to 2010. During the same time period, the FBI estimated, on average, more than 16,000 homicides across the United States (www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2010/crime-in-the-u.s.-2010/tables/10tbl01.xls). These estimates suggest that gang-related homicides typically accounted for around 12 percent of all homicides annually."