I don't know exactly how police work goes, but I find it somewhat counter-intuitive that the police felt that this van was a good match. It wasn't the right manufacturer (Ford or GM), color (white vs. off-white + trim), or even body style--this was unibody while the suspect vehicle was clearly body on frame.
Later reports indicate that the van had (surprise!) nothing to do with the shootings. Fortunately, they did pick up a couple of suspected illegal immigrants and have scheduled them for deportation.
(which appears to be better than the INS has been doing)