A new docuseries about the murder of Mexican American singer Selena Quintanilla Pérez is stirring controversy among fans and her family. The two-part series, “Selena & Yolanda: The Secrets Between Them,” which debuts on Oxygen on Saturday, features extensive interviews with the singer’s killer, Yolanda Saldívar from prison. Saldívar was convicted of first-degree murder in 1995 and is serving a life sentence. (Oxygen is owned by NBCUniversal, the parent company of NBC News.)