If your theory is right the police may want to check the videos of businesses that do have cameras since the killer would case the place first.
He has been casing the places, and from nearby videos, they’ve turned up a guy with a duffel bag at two of the places (which aren’t near each other). He obviously knows at what time the store is likely to be empty, etc.
The first drawing they released showed a black guy, but the man in the video appears to be white and possibly, in my opinion, middle eastern himself, possibly a Turk or an Egyptian. However, he may have nothing to do with it and could possibly be a supplier or somebody who had a reason for being at these stores.