Near as I can tell; you surrender, until this annoying buzzer sounds, then you change your mind, then run, shoot using horrible tactics, run some more, reload standing in the wide open, run some more, disarm yourself while standing in the wide open, change guns, shoot some more standing well framed in a door or window, reload while standing in the wide open, then repeat. Oh, and if it is a well constructed course, you will probably get to shoot from a portal on a barricade where you stick your gun through it before engaging.
Great fun. It is like an ultra compressed class on how to get killed in a gunfight.