Being attacked by a gun wielder is a scary event. The damage is great, and the thunderous noise of each shot is horrifying. After 4 rounds of dealing with this situation you may be required to make a Mental Balance check against being Shell Shocked, at the GM's discretion. If you are an ally of the gun wielder, the check is an Easy Mental Balance check, simply because you have grown used to the noise. If you are someone who is facing off against the gun wielder it becomes a Hard Mental Balance check. GM's may rule otherwise, depending upon the situation. Shell Shock inflicts Fear and Anxiety on the afflicted anytime they hear a loud noise.
Shell Shocked requires a game week to go away. Until then the symptoms of Fear and Anxiety can be treated.