From Halopedia, the Halo wiki
Oscar-129 was a Spartan-II supersoldier. In 2525, Oscar and four other Spartans escaped from Reach to return to their homes. Oscar learned that his kidnapping had been covered up by replacing him with a flash clone. He was overwhelmed by this revelation and committed suicide, his body being recovered by the Office of Naval Intelligence soon after.
Oscar was one of 75 children who were selected by Dr. Catherine Halsey for in the SPARTAN-II program. He was taken from his home in New Houston in 2517 and was trained on Reach for eight years. Oscar survived the augmentation procedures but sought to return to his home.
Escape and suicide
Shortly after recovering, he and four other Spartans (including Daisy-023, Ralph-103, and Joseph-122) escaped the training facility and stowed away off-planet. Arriving home, Oscar discovered that his family did not know he had disappeared. His abduction had been covered up by having a flash clone take his place. The clone had deteriorated physically and was now in a wheelchair. His family did not get a good look at him and called the police, reporting that a stranger had broken into their home only to panic and flee. Oscar used his sidearm to commit suicide a while after he left, feeling there was nowhere left for him to go.
His body was discovered by unit Seven-Charlie-Nineteen of the New Houston police, who was confused to find the body of the child from the home he had just visited. He found Oscar's Spartan tag and called for further investigation, but his dispatch received a call from the Office of Naval Intelligence telling them to turn the matter over to ONI. Oscar's body was recovered and the incident remained covered up until 2558, when conspiracy theorist Mshak Moradi discovered the police record.
List of appearances