Pretty obvious aimbot, looks like he has it set to hit chest or something.  It's really obvious when he got the ak and was camping ct spawn.  Also, toward the end of the demo when he had the machine pistol he does a complete auto-180 and kills some guy on Short.  You can also tell by the way his crosshair resets after the aimbot turns off.
http://www.mediafire.com/?7scxwsce37l8k3x