Walls and potentially aimbot, 98% sure.

https://www.youtube.com/playlist?list=PLAVS_0JcVJe-Kmud3S4QZxlUrNsbFTKJ_

Scans walls and goes to people, quite a few snaps from 1 player to the next after a kill.

Accuracy 50% higher than normal for HC gungame, the norm is around 18%, the high norm is 30 for pistols and 27 for troll... This was DLC which maxes around 25... at 34% that along is suspect.

Please do not compare Normal gungame and HC gungame for accuracy %... the bullets required for killing in normal naturally lead to higher %.

Adding more footage since he hasn't been banned yet.  

https://www.youtube.com/watch?v=xAMfQeDj20c