They said that it was an expired tag.
I seriously doubt there was a legitimate reason for pulling this driver over... other than to fish for a summons to write.... wasn't the truck registered in North Carolina? He probably saw out of state plates and revenue opportunity. NC plates... at least that's what I thought I heard when I saw the video one time yesterday. I could be wrong...
Point is... there was most likely no intentional criminal activity going on... they were looking for a DUI... and if it wasn't a DUI it would be something else. Seatbelt... weaving... not using a turnsignal... anything to justify initiating what turned into a shooting incident (for whatever reason).