"Glass from shattered car windows and storefronts littered the ground, whipping demonstrators along with tree branches and trash, video and interviews show. "

"Dirt and grit collected in mouths. Anyone without goggles had trouble keeping their eyes open. The roar of the blades was deafening. To calculate the approximate altitude of the Lakota [helicopter], The Post used geospatial data, building elevations, street widths and measurements of other street objects to create a precise scaled model of the intersection. It also used metadata from a photograph of the helicopter taken at 10:03 p.m. in the same spot to further build the 3-D environment. Sam Ward stood on 5th Street NW and watched the Lakota blast the nearby trees into a frenzy. 'It was pretty wild, and it certainly appeared they were using it as an intimidation tactic,' Ward, 27, said.... [T]he use of a helicopter’s rotor wash is a common military tactic to incite fear, disperse crowds and warn of other capabilities, like rockets and guns, said Kyleanne Hunter, a former Marine Corps pilot who flew Cobra attack helicopters in Iraq and Afghanistan.... [T]he Lakota had an estimated 48 mph rotor wash.... That force was strong enough to snap a thick tree branch outside the National Portrait Gallery, a Smithsonian official said."

From "A low-flying ‘show of force’/Two military helicopters roared over demonstrators in Washington protesting after the death of George Floyd, producing winds equivalent to a tropical storm" (WaPo)(analyzing events that occurred on June 1st).