First of all... great game huh?

Yesterday I was playing and I came across something that might be a cheater. Playing Spears this one player (not to mention name) would come up behind me if I ever stopped running and kill me . After the first couple of times, I started running to absure parts of the map and sure enough he found me. I think he got me 9-10 times, and even when I was expecting him (and I am not a noob).

Is this a hack?? What hacks should I be looking for??
Thanks-

Do you understand the concept of crysis in-game radar? When someone from the enemy team collects 3 dog tags, they have your positions on their radar, which allows easy tracking. You can even track and kill cloaked targets with some experience.