On a street in Rochester, N.Y., earlier this month, police and demonstrators clashed violently, with marchers shouting and coughing as officers in riot gear fired pepper balls at the crowd.
As tear gas fogged the intersection, a Black protest leader urged white demonstrators forward.
"If you're a white person, you're getting to the perimeter, you're putting your body on the f****** line right now!" she shouted to a group of protesters wearing goggles, filter masks and bicycle helmets.
They responded by hustling forward, forming a line with homemade shields.