An 11-year-old Colorado boy was arrested for the murder of his 5-year-old little brother on Wednesday.The unidentified kid faces charges of first-degree murder, although officials revealed few details of the Tuesday night death that rattled the affluent suburb of Centennial, near Denver.“This is an open and active investigation … Because both the victim and the suspect are minors, the information we release will be limited,” the Arapahoe County Sheriff’s Office said in a Wednesday statement.Horrified residents of the quiet, family-friendly