The Nipton Massacre resulted in a great loss of life, with just four survivors: The winner, Oliver Swanick, the second place runner-up, Boxcars, crippled with hammers, and two Powder Gangers destined for slavery east of the Colorado. The Courier can choose to save them from their fate.
Releasing the Gangers will cause the legionaries to attack. Unless the player wants to gain infamy with the Legion, the legionaries need to be eliminated in Sneak mode. The freed Gangers will then flee towards the old nuclear test site, where they are liable to be killed by the high-level ferals prowling the area. If the ghouls are gone, they will stay there until they respawn - and then die.
It's possible to auto-complete the quest by freeing them beforehand and then talking to Boxcars in Nipton.
Note that completing this quest with Craig Boone in tow will advance his quest line. Boone will automatically attack any legionaries he detects. The player can avoid infamy by entering sneak mode. As long as they remain undetected, no infamy will accumulate. Alternatively, clearing the camp out then bringing Boone also works.
Rescue the captives.
PCPlayStation 3Xbox 360 Scripts and NPC behavior can bug out in a variety of ways, including the Gangers returning to a kneeling position, walking around freely before being untied, followers attacking Gangers based on the player's reputation, and so on and so forth. Saving before approaching the camp helps.