On June 4, 1977, while Puerto Ricans in Chicago are celebrating Puerto Rico Day with a parade, a bomb detonates in a city government office, but causes no injuries. It is one of about 100 such bombings carried out nationwide by the FALN, a militant group agitating for Puerto Rican independence, in the 70s and 80s. Hours later, police — claiming to be responding to reports of gang violence in Humboldt Park, where many Puerto Ricans are picnicking — shoot and kill two men and soon find themselves under attack by an angry mob. Riots ensue for the next day and a half. Police in riot gear are unable to clear the streets. Violence prevents firefighters from putting out fires. Over 200 people are arrested, and countless injured, including over 50 police and firefighters.