I believe this individual was wall hacking. Watch the demo. There are several instances of him knowing where people are over the wall in cs_compound. Near the end of the demo, he blatantly displays his wall hack. Particularly the head shot of the T on the upper walkway just as he comes out into the window.

Hit shift+f2 to control the demo. Type sv_cheats 1 and then mat_wireframe 1 in console to really see what I'm talking about.

If you have doubts, please message me or discuss it here. I confronted this person about it before banning him and he denied it.

Please watch the demo.

Other players in game were also complaining to me about him and that they thought his game playing wasn't on the up and up.

EDIT: Please message me for the demo. I will email it on request. I can't upload it because I get an error saying that a security token was missing.