If this is our guy, I doubt he gets close enough to be seen on a surveillance camera, even in daylight. He's too careful for that.
Based on our previous experience with these terrorists, I'd start checking speeding tickets in the vacinity of all the shootings. This guy plans carefully and has probably driven his route beforehand. If he's like our 9/11 kooks, he's probably been speeding on the interstate in these counties--and may well have unpaid tickets.