same thing happened to me TWICE online yesterday. people who walk through walls usually get inside textures and snipe people. but this time, shots came from several walls, even opposing ones. so i reviewed the cinema and followed this guys. both times, they were playing fine, but suddenly, they respawned, and died inexplicably. The follow camera just froze on 1st person mode the rest of the game, so i replayed the video from free camera and their bodies just warped and remained dead the rest of the game. however, shots were fired from several walls, and even mid air. They even punched some guys.
Since the camera didn't follow, i don't know what happened (unlike traditional wall glitchers, whom you can see shooting though textures).
So, glitch? cheat?
I saw two different guys do it, but only once in several games, and they even died, and respawned in the same situation.