Monster And NPC Death
Most monsters and NPCs don’t have Resolve Points, so injury and death work differently for them. A monster or NPC reduced to 0 HP is dead, unless the last bit of damage it took was nonlethal damage (see page 252), in which case it is knocked unconscious. If it is ever important to know exactly when a monster dies, such as if you want to capture the creature alive, the GM can decide that a monster reduced to 0 or fewer Hit Points with lethal damage dies in 3 rounds unless it takes any additional damage or receives healing. If a monster or NPC has Resolve Points, the GM can choose whether the monster dies at 0 HP or if it uses the normal rules for dying and death.
Source
Core Rulebook pg. 250