Developing now. Tragedy in Chicago, four passengers on an L train are dead and a suspect under arrest after a mass shooting spanning two train cars in a Chicago suburb. Police say the shooting happened on a blue train. Blue line train that was heading from Chicago was o'hare Airport to the suburb of Forest Park. Three of the victims died on the train. Another was taken to a nearby hospital where they later died. The shooting so far police say appears to be random and that there is no known motive, a horrible situation. You know, it's definitely something that you don't want to wake up to. You know, it's a Monday morning on a holiday. Police are not yet releasing the names or ages of the victims. Investigators say surveillance video led them to the suspect who was on a different train.