Meu Tio Matou um Cara (2004)
Meu Tio Matou um Cara ("My uncle killed a guy" in Portuguese) is a 2004 Brazilian comedy film. It follows the adventures of Duca (Darlan Cunha) and his two friends after his uncle, Eder (Lázaro Ramos), shows up and confesses to his family of having shot a man. However, the 15-year-old Duca suspects that his uncle's story about killing his lover's ex-husband in self defense is not entirely truthful and so sets out to solve the mystery.
More at Wikipedia.