I dunno, it all strikes me a bit too convenient at this point, I'm in the wait and see mode.
If it turns out that these are not the perps and they are released, that could become a an interesting scenario in its self.
Currently, it looks like all they have is an "anonymous tip", which could just be from somebody who doesn't like them.
Could be the cops did a bit of data mining that they don't want to draw attention to, like checking cell phone records to see who was in each area at the time of the shooting (the cell phone system has to continuously know which cell tower your phone is nearest to in order to route incoming calls to your phone -- without doubt Homeland Security has mandated that phone companies permanently retain such data) and cross checked it with car ownership records of matching car types and DMV records(to look up the race of potential suspects).