IMHO, this is another signal that this is the work of terrorists, and not a simple psycopath. The timing of the shootings makes sense for terrorists as well. First, a rash of shootings to get the media's attention, then enough to keep it in the public eye while minimizing risk to the shooters.
If this is the work of terrorists, the response should be to give no more information about unsolved homicides to the press, because that is what the terrorists want. There response to this tactic would predictably be to create another rash of shootings to force it back into the public view.