Whether he intended to or not, that would be the effect of what he did. The police had roadblocks looking for the cream-colored van and likely the murderer just drove off in some other vehicle.
I wonder if the police know who he really is, or is he part of the plot and he give them a fake id. I haven't had the time to look at all the threads to see if that issue has been addressed.
I tend to think he is not part of the plot because cnn.com (I know, I know) is reporting that sources say he was in the store at the time of the shooting. If he was part of the plot, you would think he would pre-position himself in a location that would make him a more believable witness.
If his actions aided the escape in any way, I think he should be charged as an accessory after the fact to murder.