EpicAgentJ
Offender: oClayton
They were using some sort of invisibility hack.
Evidence:
Note: At one point when the victim trying to kill the hacker in the game, you can see on the chat it says "...by oClayton"

 

This appears to just be a visual glitch on your side, you can see that the zombies are attacking this "invisible player" indicating that they can see the player. I'd just relog if it happens and it should fix the issue.

 

Thank you for the report.
Unfortunately the evidence provided is insufficient.
Should you gain more evidence in the future, do not hesitate to report this player(s) again.

Kind regards,
The Staff