Here is a picture of the Fairfax County Police officers (maybe not all)..Look at the badge on the arm of the ones in blue...looks like the same badge
http://www.fairfaxcounty.gov/police/
then look at the video of Officer Cheeks Jr again (at approx 24 secs.) Looks like the same one to me.....
It looks the same to me too.
His shoulder patch reads “______ County Public Schools.” I just can’t make out the name of the county. Probably Fairfax.