Panic reload
So when a guy died by got mauled (aka 4 zombies swarming him and he screaming upon death) teammate nearby that poor lad has a 15-20% chance to perform a "panic reload" if they reload their gun in 5 seconds after that guy dead
Panic reload: you reload your weapon 30% faster, but that shot accuracy is decreased by 40-50% and you have 20% chance to "misfire"
Misfire: basically you aim your gun and shoot but it failed to shoot. You have to aim then shoot again, the 2nd shot is guaranteed to shoot.
So yeah that's my suggestion, hope it's not too bad.