What was the real reason for the Haymarket Riot?

What started as a peaceful march for labor reform ended up into a violent conflict  An unknown person threw a bomb at the Haymarket Square in Chicago during a labor demonstration resulting in a violent riot. The bomb was thrown at the police when they attempted to disperse the crowd. This makes it seem like a rebellion against authority, but the jury saw it differently. The statement given said, "The evidence has shown conclusively to us that these men were manipulating this agitation from base and selfish motives". But an example that the jury gives states, "their plan was to involve, so far as they could, not only the Socialist and Communist organizations with whom they claim some kindred, but also the labor societies... in the midst of the excitement they were creating they could not only rely upon them as a source of revenue". Looking back on this issue from today's stand point makes me think that this blame is just a result from the fear of communism prevalent at that time. It doesn't make much sense that socialists would be leaching off of labor unions when they both want equal treatment in the work force. From this limited information it makes me think that the Haymarket Riot was just the result of frustration from a work force.