Detailed Explanation
In one of television's most shocking reveals, the killer was Ryan Ross—a 13-year-old boy who shot Erin to protect his family. Ryan discovered his father John Ross was having an affair with the teenage Erin (who was also the mother of John's secret baby, DJ). When Ryan tried to confront Erin with his father's gun, the situation turned deadly. The reveal was devastating because Ryan was a child trying to save his parents' marriage, not understanding the full consequences of his actions. His mother Lori's decision to cover for him, and Mare's discovery of the truth, forms the emotional core of the finale.