My friend and i were near the NEAF when all of the sudden i see two of him, a guy right behind him. I thought it was lag for a second. His body dupping and disapearing. Or someone that logged in.

But the guy who kept disapearing had a mask and a mosin, none of which my friend had.
This freak teleported behind us, untill he killed my friend. I had no chance to shot him, he was only visible for a split second...