Spectator Hack?

So, i was playing in a seemingly normal server and i saw this one guy running around playing but it said he was a spectator and he didn't die once. Next match, he was on the other team at the start but he became a spectator but, he was running around killing people and i unloaded a whole clip in him and he didn't die. then i asked him how he did it and he kicked me

Very odd indeed

Yeah read about that, would like to know too :P

Yeah, it was pretty cool. he did different server hacks like changed the speed and made it so we couldn't move