The event occurred around 6am on Christmas morning. The victim was a 40-year-old bus driver. "We're going to end badly," Rafael Horacio Moreno, a 74-year-old retired Federal Police officer, warned a group of neighbors who were celebrating Christmas on a street in the Buenos Aires town of Lomas del Mirador, La Matanza district. The pensioner, annoyed by the volume of the music, rebuked them. Then, he took his gun and shot one of them dead. A video, which emerged in the last few hours shows the complete sequence of the attack and is for the moment the key evidence against the murderer.