Blatant Aimbot and walls. Snapping, firing at walls, etc.

Video Evidence:

https://youtu.be/n2IZY_N9SMs

https://youtu.be/JviaMefpRrI

Or if you'd like a slightly quicker disposition, here's two battlereports with very high HSKR:

Locker with M98, 15 headshots, 22 kills and 46% accuracy, in ~6 mins: http://battlelog.battlefield.com/bf4/battlereport/show/1/1029131142461426176/573296165/

Locker with M98, 25 headshots, 29 kills and 19% accuracy in ~10 mins: http://battlelog.battlefield.com/bf4/battlereport/show/1/1029081818755009024/573296165/ 

Quick link to last 20 battle reports (source for length in rounds: http://bf4cheatreport.com/?pid=&uid=XPEHOMET2000&cnt=20&start=&startdate=&rid=