Outrage over the fatal shooting of an African-American teenager is giving way to anger that the white police officer who pulled the trigger might never face justice.
Several dozen protesters gathered on Wednesday at the St Louis County prosecutor's office, calling for Ferguson police officer Darren Wilson to stand trial for the death of Michael Brown, 18.
Inside, a 12-member grand jury began hearing evidence. It could invite Wilson to appear, county prosecutor Robert McCulloch told St Louis news media. Grand juries meet behind closed doors to determine if there is sufficient evidence for an indictment leading to trial.
Nearby, US Attorney General Eric Holder, on a day trip from Washington, mingled with Ferguson community leaders and residents, as a federal Justice Department civil rights investigation into Brown's death rolled on.
Many African-Americans dread the idea that Wilson, 28, a police officer for six years, might not be charged.
"I honestly believe this is the beginning of a cover-up," said Jerryl Christmas, an African-American lawyer in the St Louis area, amid growing calls for McCulloch - whom critics say has a track record over two decades in office of not going after police wrongdoing - to be pulled off the case.
Wilson has not been publicly seen or heard since Brown, a suspect in the theft of a box of cigars, was shot at noon on a residential street on August 9.
Colleagues and friends said Wilson opened fire after a struggle with Brown, while other witnesses claim Brown had put his hands up in surrender when he was shot six times.
Brown's family has led calls for Wilson's arrest, saying he "executed" the youth, while street protests in Ferguson have degenerated into violence.
Nationally, "although black men made up only 27.8 per cent of all persons arrested from 2003-2009, they made up 31.8 per cent of all persons who died in the course of arrest, and the majority of these deaths were homicides", the American Civil Liberties Union has reported.
"It's hard for a community to have confidence in a system that only prosecutes them," said Christmas, a one-time prosecutor and a leader of an orderly protest on Wednesday.
Christmas pinned part of the blame on a significant lack of African-Americans in key positions throughout the criminal justice system, from police officers to judges. "Look at all these police officers," he said, gesturing to the dozen or so Clayton city officers at the demonstration. "How many African-American officers do you see?" (The answer: one).
A Justice Department report said blacks as well as Hispanics were three times more likely to be searched during a traffic stop than whites, and four times as likely to experience the use of force in encounters with police.