S1 E2: The Masked Murder

Claudia and her roommate, Victor, spend the evening with her twin brother Claude. At some point, during the evening, tragedy strikes, and Claude is shot dead. When the police question the witnesses, Claudia states, "Victor and I heard the sound of a fight coming from the library. We walked in just in time to see a man in a mask shoot my brother, then run out the French doors. Victor chased after him." The maid confirmed the last part of Claudia's story. Although the gun was never found, Claudia was eventually arrested for her brother's murder. Victor, an innocent dupe, was exonerated. How was Victor duped into helping Claudia commit murder? What happened to the gun?