Killer calmly confessed to suffocating his wife, her 2 girls with a plastic bag

After a week of already grueling testimony, jurors in the death-penalty case of Alberto Sierra heard the killer calmly detail to detectives exactly how he snuffed the lives of his estranged wife and her two young daughters with a plastic shopping bag.Miami-Dade Det. Juan Chaidez testified that he took Sierra’s confession on Nov. 19, 2012, more than a week after the Nov. 10 murders of Gladys Machado, 29, and her daughters Julia Padrino, 6, and Daniela Padrino, 3.