Protests have taken place in more than 100 US cities, a week after George Zimmerman was cleared of murdering Trayvon Martin, an unarmed black teenager.
The BBC reports demonstrators want federal charges to be brought against George Zimmerman, 29, a neighbourhood watch volunteer, over the incident.
A jury in Florida found last Saturday night that he killed Trayvon, 17, in self-defence.
The protests against the court's decision were led by the National Action Network, headed by civil rights activist the Reverend Al Sharpton.
"We are not coming out with violence, we are coming to denounce violence. The violence that was perpetrated on an unarmed, innocent man named Trayvon Martin," Mr Sharpton told at a rally in New York.
Thousands gathered for "Justice for Trayvon" protests in at least 100 other cities across America, including Atlanta, Chicago, Los Angeles and Miami.
Mr Sharpton told supporters on Saturday morning that he wanted to see the scrapping of "stand your ground" self-defence laws, such as that in force in Florida.
The teenager's mother, Sybrina Fulton, told the crowd: "Today it was my son. Tomorrow it might be yours."
Trayvon was shot dead by Mr Zimmerman after an altercation in a gated community in Sanford, Florida on 26 February, 2012.
Last Saturday, a female jury of six found him not guilty of second-degree murder and manslaughter.
