A Better Tomorrow
Most damage is assumed to be nonlethal. Attacks can also inflict lethal damage, capable of seriously wounding or even killing an opponent.
Any damaging attack can inflict lethal damage. The attacker must declare the intention to inflict lethal damage before the attack roll.
Depending on the style of the campaign, declaring a lethal attack may be quite un-heroic. Generally speaking, heroes rarely, if ever, make lethal attacks, while villains seldom do so, preferring to defeat heroes and stretch out their final moments with some fiendish trap.
Lethal damage is handled the same way as nonlethal damage, except a failed Toughness saving throw applies an additional damage condition:
a bruised target is also Injured,
a staggered target is also Disabled,
an unconscious target is also Dying.