Protesters set cars on fire with flares during the second day of the G20 Summit in Hamburg, Germany, on July 7. At the start of the summit a day earlier, police used water cannons in an effort to disperse demonstrators.Heavy security was present from the outset, as police on Thursday warned protesters their planned rally would not go ahead unless people removed face masks.This video shows masked people breaking car and storefront windows and setting cars on fire with flares. Credit: Extinguisher TV via Storyful