Everyone who has "the drop" or some other surprise situation one free 3-shot action, as if it was the end of a sequence, and they had 1 shot left while everyone else has zero.
If the target is caught flat-footed, he cannot use his Dodge to defend, makng the difficulty of the attack Agility instead. In even more extreme cases, when the target isn't expecting danger at all, the defense is zero.
THis si an area of the rules that is very much open to interpretation and dramatic effects.