The low wages,cut backs and lay offs
What Was The Immediate Cause And Underlying Causes Of The Haymarket Riot? What Were The Immediate And Long Term Effects?
The Haymarket Riot on May 4, 1886 in Chicago is considered to have been the main influence on the origin of international May Day observances for workers. This event inspired the caricature of "a bomb-throwing anarchist." The cause of the incident are still controversial, although deeply polarized attitudes are generally acknowledged as having precipitated the tragedy and its aftermath.
Don't know thats y I'm asking you
There is a good overview in britannica.com which looks at the background and context as well as the riots themselves and the trial.