Hit her in the eye region just right. Probably wasn't even a fan, just happened to be a gawker in a rowdy knot of students.
According to Wikipedia, the mfg claims the flash-ball hits with the "stopping power" of a .38 handgun.
That shooting incident in Boston during a sports victory celebration? The young lady killed was from Bridgewater, MA (about 30 miles south of Boston, in its fan-sphere) and an undergraduate student. There was absolutely nothing negative in her background, just a girl out with her friends, celebrating an awesome Boston victory.