Want Revenge? Impossible! I'm a Genius Detective

Three years ago, Chen Xuan subdued a robber. The robber stole money to treat his mother's illness, but Chen Xuan was imprisoned because of it. Three years later, the robber was released from prison and his mother died because she had no money for medical treatment. It was because of Chen Xuan that the robber hated Chen Xuan. So one morning, I set my sights on the school with premeditation. After Chen Xuan arrived at the scene of the crime, the murderer called Chen Xuan to tell him that the child's death was because of Chen Xuan. He wanted Chen Xuan to regret in his extreme self-blame state and regret that he should not have stopped him back then.