I have had several occurrences where I have been killed by other players right next to me and there was no audio of them. No footsteps approaching, no sound of gun being handled, just complete silence. I knew they were right next to me because I heard the gunshot right next to me before the black screen. This has happened to me several times now. I'm not sure if this is a bug or someone hacking. But one example of this was me fighting a zombie and looking all around me while doing it, so I had view of the entire area, no players were in sight, then all of a sudden, a gunshot. I know this is a bug/hack because when I team up with other players, I can hear their footsteps just fine when they walk next to me. But somehow, enemies footsteps make no sound whatsoever.