I was told hitmarkers are confirmed serverside hits, I got 5 on this guy with the SVD-12, which is a 3 hit kill at that range. I'd also been killed by this guy before after scoring 2 hits and he had 100hp left.

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

https://www.youtube.com/watch?v=3b1gKJRkq1k

This guy is 100% Cheating/Hacking he used speed run in the server. 

Above you see on the end in the kill cam. you cant kill him. https://www.youtube.com/watch?v=3b1gKJRkq1k

http://battlelog.battlefield.com/bf4/battlereport/show/1/934343437909806528/346639496/

http://battlelog.battlefield.com/bf4/battlereport/show/1/933339419183112384/346639496/

http://battlelog.battlefield.com/bf4/battlereport/show/1/934336020903939520/346639496/