A 30-year-old man from Chicago has been accused of murdering four passengers who were shot while sleeping on an L train in Forest Park, Illinois. The suspect, Rhanni S. Davis, is facing four counts of first-degree murder. The authorities described the incident as a random act of violence, with the victims being shot as they slept on the train. The shooting took place on a westbound Chicago Transit Authority Blue Line train, and surveillance footage showed the assailant walking through the train and shooting the victims. Three men and one woman were killed, and another potential witness fled the scene. The suspect was apprehended by the Chicago police on a Pink Line train, and a handgun was recovered during the arrest. The president of the C.T.A. called the incident a heinous crime and tragedy, emphasizing the complexity of addressing violent crime on the public transportation system. The suspect is expected to appear in court, and the authorities are still searching for the potential witness who fled the scene.