YEAH.  No shit.  ONE concealed carrier may not be able to halt a determined assailant.  It is hard for a civilian to shoot to kill properly.  However, suddenly having bullets flying BACK at the shooter WILL, WITHOUT DOUBT, disrupt the shooter's concentration and his ability to move forward unabated.  These vital seconds can save lives.  Stalling the shooter, even for only a few moments aids the police.  It is a CRYING DAMN SHAME that none of the congregates was armed.