I think Wavemaker's implication here is that the perpetrator is assuming the victims meet some criteria.

A narrative that I've speculated (based on what little information is available) is that it is possible that an altercation took place between someone and Kevin.  Maybe Brie was in the area (possibly playing Pokemon go?) and heard the altercation.  I wouldn't put it passed a community activist to set aside personal fears in an attempt to resolve a disagreement.  I realize at this point it is purely speculative.  I am offering this scenario as a possible explanation of how these two individuals paths may have crossed.

One thing is clear, Justice must be served.