James Valentine is the murderer of Francisco Ariza. Valentine was a juvenile when he was sent to the Army to avoid prison time. After which he stayed clean and he worked for Pops Walters. Valentine warned Pops about Ariza knowing Ariza was mean and violent towards Pops. When Pops was murdered he was questioned by police. Before the shooting Valentine stole some money from Pops so he can buy Pops a gun to defend Pops from Ariza.