Task: Question Answering
Input (English): Passage: Sergeant First Class Buck McGriff and Sergeant First Class Albaby Perkins are two joint services Criminal Investigation Division agents on duty in war torn Saigon.  When a prostitute is found murdered they discover that the prime suspects are high ranking U.S. Army officers.  As they investigate they find that there have been a string of at least six murders in the last year, but the previous inquiry was shut down from higher up the chain of command. Investigations lead them to Colonel Dexter Armstrong, but Armstrong rules himself out of inquiries by committing suicide. With the help of a French nun Sister Nicole and their non-commissioned officer in charge, Master Sergeant Dix, they finally close in on their target. As their investigation leads them closer and closer to the murderer, they find their lives are in danger and they end up nearly being sent home. The movie ends with an unexpected twist when they rule out all their suspects by conducting an interview in a Viet Cong tunnel base, and their NCO is the killer. 
Question: Whose NCO is discovered to be the murdered?
Output (English): Viet Cong.