You must be watching a different video then I am. The video was so choppy I never saw the player fire a gun once.
As for the extra speed, looks to me like the internet was acting up in his favor.
You cant prove hacking in a ten second clip. There could be MANY reasons why that happened.
He moved like how you would controlling a free-roam killcam. Classic movement for a hack. Plus that last kill demonstrates that he was not worried about getting shot, despite that other guy emptying his clip, he didn't move and just hip fired him. Again, classic evidence of God Mode.
So it begins the comprehensive (v. just a scorestreak or movement) hacks. Once it begins, and with the Dev's history of slowly but surely becoming either unwilling to deal or ineffectively dealing with it, be ready to see it more and more.
Hacks surfacing this late in the game cycle is not necessarily a bad thing for the Devs. They give consumers that little extra nudge to buy the new title.