CSI: Crime Scene Investigation Episode 10.19 World's End

When Lindsay, Katherine's daughter, is playing the lead in her high school's version of Cabaret, a gruesome murder is discovered on campus. A young man who was not well liked at the school turns up dead in the storm drain. He was a racist and a part of a white supremacy group of boys who commited hate crimes. There are multiple murder suspects and then the story takes a sharp turn as we learn that he had actually befriended the African janitor at the school. He became interested in the janitor's history as a refugee from war torn Rwanda. The man relayed his terrible stories of genocide and losing his entire family to the horrors of the war which hit a cord with the young boy. But when the boy found out the man was lying, and that he actually was one of the mass murderers who had moved to the U.S. and changed his identity, the boy went after him. The janitor killed the young man to keep him from exposing his secret.