Liberal or not those aren't sources, they are mostly opinion pieces.
This may be a better source
https://leb.fbi.gov/2014/january/active-shooter-events-from-2000-to-2012
which summarizes for active shooter events ' Shooters did not fit a specific profile. While most (94 percent) of the shooters were male, some were female. They also came from different racial and ethnic categories. The youngest shooter in the data set was 13, and the oldest was 88. Again,
no clear profile based upon the demographics of the shooter was observed.'
In a broader context, also refer to For 2013 FBI crime Statistics (
https://www.fbi.gov/about-us/cjis/uc...ables/table-43), for arrests, which Black or African American comprised 4,379 murder arrests out of 8,383 in 2013, or 52+ percent of the arrests.
The US Census for 2013 (
http://quickfacts.census.gov/qfd/states/00000.html) indicates black or African American comprise 13.2% of the population.