Answer:
The Haymarket protest turned violent when a police was bombed.
Step-by-step explanation:
The Haymarket protests had been instigated by the workers as labour protests for worker's rights. Following the riots and killing of people, a meeting called by labour leaders which included police, strikers and the Chicago Mayor had been called.
While the meeting was deemed peaceful, things got worse. Dispersing the crowd after the meeting resulted in more riots when a random person threw a bomb in the air. Police and civilians were injured and killed in great numbers during the process.