During a battle with an NCR force he chose to be captured instead of committing suicide, counting on being able to escape captivity without revealing any information about Caesar's plans. The player can try to interrogate him at Camp McCarran during an unmarked side quest.
Silus Treatment: Silus is held captive in Camp McCarran, and the NCR is attempting to interrogate him. He will not give information to the NCR, and interrogator Carrie Boyd is looking for help. She informs the player that the NCR does not allow torture of prisoners. The player can suggest a truth serum, beating the prisoner, or calling him names. Silus may also be freed by a Legion player, resulting in a few special dialogue lines from Caesar.