The Haymarket affair refers to the aftermath of a bombing that took place at a labor demonstration on May 4, 1886, at Haymarket Square in Chicago. An unknown person threw a dynamite bomb at police as they acted to disperse the public meeting. The bomb blast and ensuing gunfire resulted in the deaths of 7 police officers, 4 civilians and many seriously wounded. In the internationally publicized legal proceedings that followed, eight anarchists were convicted of conspiracy. The evidence was that one of the defendants may have built the bomb, but none of those on trial had thrown it. Seven were sentenced to death and one to a term of 15 years in prison. The death sentences of two of the defendants were commuted by Illinois governor Richard Oglesby to terms of life in prison, and another committed suicide in jail rather than face the gallows. The other four were hanged on November 11, 1887. In 1893, Illinois' new governor John Altgeld pardoned the remaining defendants. The Haymarket affair is generally considered significant as the origin of international May Day observances for workers. NOTE: This engraving inaccurately shows Fielden speaking, the bomb exploding, and the rioting beginning simultaneously.