IT IS A HORRIBLE SITUATION . IT IS SOMETHING YOU DO NOT WANT TO WAKE UP TO. IT IS LABOR DAY . TO ACTUALLY HAVE TO BE HERE TO ADDRESS A SITUATION LIKE THIS, IT IS HORRIBLE . >> I JUST WANT TO ADD ONE THING . IT IS A HORRIBLE TRAGEDY FOUR PEOPLE ARE DEAD ON LABOR DAY WEEKEND. THE POLICE DEPARTMENT AND FIRE DEPARTMENT RESPONDED TO THIS LOCATION MORE THAN ANY OTHER LOCATION IN OUR JURISDICTION. FOREST CLARK IS THE ONLY COMMUNITY IN COOK COUNTY WITH TWO MAJOR TRAIN LINES THAT END IN FOREST PARK. WE PROVIDE MEDICAL AND FIRE RESPONSE. TO THE EXTENT LEADERS IN SPRINGFIELD ARE CONSIDERING ANY KIND OF CTA MASS TRANSIT ORGANIZATION. WE WOULD ASK THEM INFORMATION TO PASS ALONG . >> WE HAVE BEEN LISTENING INTO A PRESS CONFERENCE FROM FOREST PARK LEADERS ABOUT FOUR PEOPLE SHOT ON A MOVIE CTA TRAIN THIS MORNING IN FOREST PARK . WE ARE TOLD THAT THERE IS ONE SUSPECT IN CUSTODY. ASAL REZAEI HAS BEEN COVERING THIS STORY ALL MORNING AND JOINS US WITH MORE ABOUT WHAT UNFOLDED AT THE SCENE . ASAL? >> Reporter: THEY NEWS CONFERENCE WRAPPING UP BEHIND ME MOMENTS AGO . ALL FOUR PEOPLE SHOT WERE PASSENGERS ON THE TRAIN. IT HAPPENED WHILE THE TRAIN WAS IN MOTION. AS THAT'S TRAIN WAS HEADING INTO THE FOREST PARK STOP AND BOUND FROM O'HARE. WE ARE TOLD IT HAPPENED ON TWO DIFFERENT TRAIN CARS JUST BEFORE 5:30 THIS MORNING . POLICE AND FIRE RESPONDING . THEY SAID THREE PEOPLE WERE PRONOUNCED DEAD ON THE SCENE AND A FOURTH PERSON WAS TAKEN TO AN AREA HOSPITAL , WHERE THEY LIVED OR DIED. FOREST PARK POLICE WORK WITH THE CTA SECURITY TEAM AND WERE ABLE TO TRACK DOWN THE SUSPECT WITHIN A COUPLE OF HOURS THROUGH SURVEILLANCE VIDEO AND CPD FOUND THE SUSPECT ON A PINK LINE TRAIN AND TOOK THEM INTO CUSTODY. THEY REMAIN AT FOREST PARK POLICE DEPARTMENT RIGHT NOW. FOREST PARK DETECTIVES ALONG WITH THE MAJOR CRIME TASK FORCE NOW TAKING OVER THE INVESTIGATION AND THEY DO BELIEVE THAT THIS IS AN ISOLATED INCIDENT AND NOT ANY LONGER A THREAT TO BE PUBLIC. WE DO KNOW THE BLUE LINE TRAIN IS SHUT