As the crowd gasped and screamed, the man, later identified by local media as 29-year-old Dallas Frazier, landed a quick volley of punches to the face of Mike Alter, 61. Within a few seconds, a police officer rushed in to handcuff Frazier.
Another protester captured video of the beating, which quickly went viral.
View the complete August 2 article by Tim Elfrink on The Washington Post website here.