Chicago police arrested a black-clad demonstrator as a protest rally broke up.
About a dozen police officers, some wearing riot gear, surrounded the protester during Friday afternoon's rally hosted by National Nurses United.
The protester was dressed entirely in black and identified himself as a 19-year-old from Albuquerque, N.M.
Police handcuffed him and walked him away from the rally on Daley Plaza amid shouts from onlookers that they had violated his civil rights.
Shortly afterward, the march headed down Michigan Avenue, and some protesters were seen knocking a police officer off his bike.