If the person or creature was knocked unconscious by the player, they may remain hostile towards the player until they get back up.
When knocked unconscious, that person or creature will fall to the ground and lay there until the battle you are in is over, then get back up. In Fallout 3 and New Vegas, unconsciousness is a result of what would normally be a death that happens to a character who is flagged as 'essential' or, in the latter, any followers while playing off hardcore. Unconscious is a condition in Fallout Tactics, Fallout 3 and Fallout: New Vegas.
