Protests have been held in several US cities after a jury found a neighbourhood watch volunteer not guilty of murdering an unarmed black teenager.
In a Florida court on Saturday, a jury found George Zimmerman not guilty of shooting dead 17-year-old Trayvon Martin in February 2012.
The trial has riveted the nation for weeks and emotions came to a boiling point as news of the verdict spread. Protests broke out in cities including San Francisco, Philadelphia, Chicago, Washington and Atlanta, with larger organised gatherings planned later on Sunday.
In Oakland, California, protesters smashed windows and spray painted cars, but most demonstrations were peaceful and closely watched by police, AFP reports.
President Barack Obama has called for calm, saying the death was a tragedy and the nation should seek ways to thwart gun violence.
Mr Zimmerman, 29, had been accused of pursuing the teenager through a gated community in Sanford, Florida, and shooting him during an altercation. His lawyers argued that he acted in self-defence and with justifiable use of deadly force.
Police initially declined to press charges against Mr Zimmerman, sparking mass protests. He was eventually arrested in April 2012 and charged with second-degree murder and manslaughter.
The BBC reports the Department of Justice said on Sunday it was evaluating the evidence to see whether Mr Zimmerman could face prosecution under federal criminal civil rights statutes, and whether such action would be "appropriate in accordance with the department's policy governing successive federal prosecution following a state trial".
A petition launched by the National Association for the Advancement of Colored People demanding that the department open a civil rights case against Mr Zimmerman received more than 350,000 signatures within hours of the case ending.