So he’s “planting” a weapon that likely has the victims prints on it, with the full knowledge there’s a witness filming everything.
Honest police officers don't move things, or drop things next to a suspect after a shooting.
http://www.evidencetrail.net/uploads/4/5/8/1/4581768/6955356_orig.png
http://i.imgur.com/DTYSXXC.gif