Mind sharing some statistics for that claim?
Sounds like you are regurgitating some hate-talk-radio host's flawed hateful email.
While there isn't a firm definition for "mass shooting" most seem to go by the 4 victims in a single event. This is based on the FBI definition of mass murder being 4 or more victims from a single assailant. HeyJackass,com compiles their own dataset via following sources: Chicago Tribune, Chicago Sun-Times, Homicide Watch Chicago, DNAInfo Chicago, Chicago Redeye Homicide Tracker(no longer updated), NBC5 Chicago, City of Chicago Data Portal and CPD CLEARMAP. To date within the city limits of Chicago there have been 17 events of 4 or more victims shot in a single event (http://heyjackass.com/2015-multi-victim-shootings/). Every instance has been black assailants with black casualties. (http://heyjackass.com/2015-multi-victim-shootings/) Chicago being my hometown, it is the only place I follow statistics closely and I cannot say that this trend holds true nationally. Also of note, within the city limits of Chicago, 78.7% of the victims of shootings are black with 68.8% of the assailants being black. (http://heyjackass.com/2015-race-of-victim/)