President Obama, Sharpton and the Rev. Jesse Jackson have urged calm. In Oakland, Calif., during protests that began late Saturday night, some angry demonstrators broke windows, burned U.S. flags, vandalized a police squad car and spray-painted anti-police graffiti.
Los Angeles Mayor Eric Garcetti urged protesters to "practice peace" after rock- and bottle-throwing. Later, more than 100 officers in riot gear converged and ordered people to disperse. A handful of people were given citations, mostly for blocking a street or jaywalking
Protesters also gathered in Atlanta, Miami, Milwaukee, Philadelphia and Washington, D.C., along with a host of other cities.
Zimmerman, 29, was acquitted of second-degree murder and manslaughter charges Saturday by a jury in Seminole County after claiming he fired his weapon in self-defense only after Martin attacked him. No evidence surfaced in the trial that Zimmerman had a racial bias, and his friends and family have repeatedly denied he harbored racial animosity toward blacks. Florida did not use its own hate crime laws against Zimmerman.
Holder's comments on the case came in a speech to the 51st national convention of the Delta Sigma Theta, the nation's largest African-American sorority, and drew strong applause with his characterization of the shooting: "We are <t40>...<t$> mindful of the pain felt by our nation surrounding the tragic, unnecessary shooting death of Trayvon Martin in Sanford, Fla., last year."
Martin's family and supporters maintain that Zimmerman racially profiled Martin and decided to follow him, leading to the fatal fight. Supporters of the Justice Department filing civil rights charges say additional evidence could exist in the federal investigation that didn't come up in the state prosecution of Zimmerman, possibly even unknown witnesses.
Several civil rights groups, including the NAACP, are demanding that the Justice Department bring federal charges against Zimmerman. Beyond the exact language of the law itself, the federal probe must navigate between sensitive racial and political issues that arose when Zimmerman initially wasn't charged in Martin's killing.
Barbara Arnwine, president and executive director of the Lawyers Committee for Civil Rights Under Law, called the verdict "a travesty and miscarriage of justice" and urged the Justice Department to bring criminal civil rights charges against Zimmerman.
Zimmerman could get life in prison if charged and convicted under federal hate crime laws.
Several former prosecutors said they'd be surprised if the department were to charge Zimmerman under civil rights laws.
"I think it would be a very steep, if not insurmountable, hill to climb and would be shocked to see any further DOJ involvement," said Jeffrey Sloman, former U.S attorney in Miami.
Sundby said the legal system does not always provide an outcome that satisfies people who believe Martin's killing was unjustifiable and morally wrong.
"That's frustrating as a lawyer to say, but sometimes the legal system -- even if there's a sense that an injustice was done -- it doesn't have an answer to that injustice," he said.