Hacking. 

https://www.247fairplay.com/CheatDetector/Komome

https://www.youtube.com/watch?v=PaiI5JE_vQQ&feature=youtu.be

There's the proof ^

2 head shots would explain the damage you received in that video.

however.....

http://battlelog.battlefield.com/bf4/battlereport/show/1/918171647237825536/1792255883/