Four people are killed in a mass shooting targeting homeless people on a Chicago Transit Authority train in Forest Park, Illinois, United States.

On September 2, 2024, a mass shooting occurred aboard a Chicago Transit Authority (CTA) Blue Line train as it traveled between Oak Park station in Oak Park, Illinois and Harlem station in Forest Park, Illinois. Four people were killed at random. The alleged shooter was taken into custody and charged with four counts of first-degree murder.

Illinois is a state in the Midwestern region of the United States. It borders Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash and Ohio rivers to its south. Of the fifty U.S. states, Illinois has the fifth-largest gross domestic product (GDP), the sixth-largest population, and the 25th-most land area. Its capital city is Springfield in the center of the state, and the state's largest city is Chicago in the northeast.

September 2 is the 245th day of the year in the Gregorian calendar; 120 days remain until the end of the year.