Active Shooter

It's clear that the three women in the bathroom don't know anything about guns. At the very least, everyone should know the 4 basic rules of gun safety. (a) Treat every gun as if it is loaded until you have personally inspected it to verify it is empty. (b) Keep your finger off the trigger until ready to fire. (c) Always know what is behind your target, to ensure innocent bystanders or property is not damaged. (d) Do not point the gun at anyone or anything you are not willing to destroy. Always have your gun pointed in a safe direction.

Everyone in that bathroom would have either lost their hearing, or had irreversible hearing damage from the gunfire that took place within. Even the single shot to Dale's groin would have given everyone at the very least strong ringing in their ears and most likely a headache from the sound of the gun going off. This is further exacerbated by the bathroom having many reflective surfaces, so sounds are amplified since the sound waves can constantly bounce back and forth from surface to surface until they are inaudible (this is called reverberation, or reverb). In the end when the shooter comes in and unloads his fully automatic weapon, no one's hearing would survive that high of a level of gunfire for that prolonged time. Also, since the shooter had been outside of the bathroom shooting indoors, he would have sustained more damage to his hearing, and would most likely be deaf by the time he went into the bathroom at the end.