Was the Haymarket Square bombing self defense

On May 3, 1886, Chicago police officers fired into a crowd of strikers at the McCormick Reaper Works, killing and wounding several men. In response, a group of anarchists met near Haymarket Square the following evening. When the police tried to disperse them, someone threw a bomb and seven officers were killed. Eight anarchists were arrested, six of whom had not been present when the incident occurred. Four were hanged, a fifth committed suicide in jail and the three others were pardoned years later.

https://www.nytimes.com/2018/09/26/obituaries/voltairine-de-cleyre-overlooked.html

https://web.archive.org/web/20181005084026/https://www.nytimes.com/2018/09/26/obituaries/voltairine-de-cleyre-overlooked.html