On July 3, 1917, continuing violence raged in East St. Louis, Illinois, as white mobs attacked black residents and destroyed their homes and other property. The primary outbreak of violence began on July 2, 1917, when white residents of East St. Louis and other nearby communities ambushed African American workers as they left factories during a shift change. The National Guard was called in to suppress the violence but they were ordered not to shoot at white rioters; some troops reportedly joined the mobs targeting the black community.
Source: On Jul 03, 1917: White Mobs Terrorize African Americans in East St. Louis Riots