I think by now that any kids -- especially if there are two -- would have been missed at school. With a 500k reward out, someone would put it together. So I rule out anyone still in high school.
The white van(s) are a bit of a mystery, but I believe the police are correct to believe that the white truck is connected to at least one shooting. I find it hard to believe that businesses in the area haven't inspected their trucks and checked their logs to see if any employees had deliveries consistent with the shootings. I lean against this being a rogue employee of a business that has a lot of white trucks.
This leaves me believing in an organized terror campaign, home-grown or otherwise -- having at least two, but possibly more participants. There may not be a political motive. It could be a Columbine style club, but they would have to have financial resourses. I lean towards believing there are political motives. The more different vehicles involved, the more I believe it is an organized group. The more different individuals involved, the more difficult for employers or neighbors to see a pattern. Any individual would have an iron-clad alibi for at least one of the shootings.
True. But what if the owner of the truck doesn't even know his truck is being used? If it's 2 brothers like I'm speculating, they would be using one of their father's trucks, an old one he isn't using anymore for his business. The father would have an alibi because he IS innocent. Same if the truck is still being used. In that case both employees and owner would have an alibi for the time of the shootings.