Lets just say, a Concentration check would be a way to clear a mind of the character. make him/her see and think clearly. Think how a Sniper would do when shooting a target. that person takes its time, checks the rhythm of that target, calculates the bullets projection and distance. takes into account bullet weight and speed velocity. The sniper can only do that with a concentrated and cleared mind. seems like all of the survivors are in a panic right now. Aiming straight alone would take alot of concentration to avoid distraction.