Ferguson - US Civil rights activist Al Sharpton has called the shooting death of an unarmed black teenager by a white police officer in suburban St Louis a "defining moment for this country".
Eighteen-year-old Michael Brown, who was black, was shot by white police officer Darren Wilson on 9 August.
Sharpton spoke on Sunday at a rally in Ferguson, where days of protest have ended with almost nightly confrontations between police and protesters.
Sharpton says he wants Congress to stop programmes that provide military-style weaponry to police departments. He says he expects police to "smear" the slain teenager, his family and his attorneys.
He also condemned the recent spate of violence and looting in Ferguson.
Reuters reported that patrol Captain Ron Johnson, entrusted by the governor with restoring order, told hundreds of people gathered at a local church for the rally that he was committed to protecting their right to protest."I'm sorry," Johnson, who is black, told Brown's family during remarks that prompted repeated standing ovations. "My heart is heavy."
Missouri Governor Jay Nixon criticised the Ferguson police department for its decision on Friday to release a video that allegedly showed Brown taking part in a convenience store robbery shortly before the shooting. Police have said the officer who shot Brown had no idea he was a robbery suspect.
"I think it had an incendiary effect," Nixon said on CBS' Face the Nation. Police "clearly are attempting to besmirch a victim of a shooting", he added.
Ferguson police chief Tom Jackson defended the release of the surveillance video, over the objections of the US justice department. Jackson said he was complying with the news media's requests for information in the case.
The decision to release the video while not giving details of the shooting only fuelled outrage. The clashes in Ferguson have pitted mostly black protesters against mostly white police in a residential and retail district.
Obama getting regular updates
President Barack Obama has been getting regular briefings while on vacation in Martha's Vineyard, including from senior adviser Valerie Jarrett.
Jarrett spoke with Nixon on Saturday to get an update and offer the administration's continued co-ordination and support with state and local officials, a White House spokesperson said. Jarrett had also been in touch with civil rights leaders, including Sharpton and NAACP President Cornell Brooks over the last few days, he said.
The US department of justice and the St Louis county police department are investigating Brown's death, which has been described differently by the police and by a friend who was walking with him at the time.
Police say that after Wilson asked Brown to move out of the road onto a sidewalk, Brown reached into the patrol car and struggled with Wilson for the officer's service gun. Wilson, who sustained a facial injury, then shot Brown a number of times.
The friend, Dorian Johnson, 22, and at least one other witness have said the officer reached out through his car window to grab at Brown and the teenager was trying to get away from the officer when he was shot. Brown held up his hands in a sign of surrender but the officer got out of his patrol car and shot Brown several times, they said.