After Flutterby's pics, I am convinced more than ever that it was the van in question, and that those witnesses had a birds eye view from the guitar shop. What I mean by this is if they were parked facing the Exxon, then yes, they would not have been able to see intricate details. However, they would've been able to see that something was awry or 'fishy'. If the perp then used that sideroad right by the strip mall as an escape route and drove right by them, which I now believe he did, then those folks would have been privy to a lot more detail at this point - especially since they suspected something was up and were paying close attention.
However, this changes things a little for me. Rather than use that route because it was on the way to wherever he was going, he could have used it simply because it was the most efficient escape. This brings in even more questions and possibilities.