All 3 (tooth, nonis, and myself) of us were pretty positive that he was cheating about half-way through the game without even needing to review the demo. It wasn't so much the kills he was getting, but the sheer amount of improvement.
Some back story on sun is that he asked nonis to play on a 4v4 team with him, which eventually got tooth and myself involved as well. He was/is a nice enough guy and most of the 4s matches were pretty enjoyable. Sun played soldier in every game prior to this one (besides one where he played medic) and he played gunboats soldier at that. There were plenty of games where we would ask sun to take more heals and play the pocket role (and use shotgun), but it was short lived because he had *self-proclaimed* "bad shotgun aim." And he did, if you look at the vods you can see his aim is really erratic and in the games prior to this one he was most likely not triggerbotting because he was missing all his shotgun.
It's really unfortunate that sun would resort to cheating, as he seemed to be playing quite a bit.