Dressed in expensive fashion, the first characters we meet in the new Netflix mini-series “Someone Has to Die” are Cayetana (Ester Expósito, “Elite”) and her brother Alonso (Carlos Cuevas, “Merlí. Sapere Aude”), who pass time shooting pigeons at their family range. Cayetana tells her brother that someone named Gabino has finally returned to marry her. He freezes. Before we can decide whether it’s out of anger or worry, Alonso takes aim, screams and shoots.