Barack Obama, the US president, has called the fatal shooting by police of an unarmed black teenager a tragedy and asked for a thoughtful response after two nights of violent protests, looting, arrests and tear gas in the US state of Missouri.
Obama on Tuesday promised a full investigation by the US Department of Justice into the case, which has provoked outrage in the largely African-American suburb of Ferguson, St Louis.
Police have not released the shooter's name, citing security concerns and death threats.
"I know the events of the past few days have prompted strong passions, but ... I urge everyone in Ferguson, Missouri, and across the country, to remember this young man through reflection and understanding," Obama said in a statement.
Friends and family of 18-year-old Michael Brown planned a peaceful church vigil for Tuesday night and his father pleaded for an end to the violence that has followed the incident.
Activists have demanded authorities release the name of the officer involved.
Standing with supporters, including the Reverend Al Sharpton, Brown's father said he wanted justice for his son but wanted it "the right way".
"I need all of us to come together and do this right, the right way," said Michael Brown Senior, who wore a T-shirt showing his son's baby picture. "No violence."
Activists speaking to reporters in downtown St Louis also called for federal authorities to take over the investigation after two nights of demonstrations and unrest.
Police in Ferguson had initially said they would release the officer's name on Tuesday but changed the plan, citing fears of retaliation, according to media reports.
Sharpton, a New York-based civil rights leader, also called for peaceful protest in the wake of looting and more than 50 arrests since the shooting. Sharpton's National Action Network will pay for Brown's funeral.
"To become violent in Michael Brown's name is to betray the gentle giant that he was," Sharpton said of the 198cm Brown, who had planned to start college this week.
Brown was shot to death in the back of a police car on Saturday, police said. The race of the officer, a six-year veteran who is now on administrative leave, has not been revealed.
The FBI has opened a civil rights investigation into the racially charged case and St Louis County also is investigating.
Police said Brown was shot in a struggle with a gun in the police car but have not said why Brown was in the car. At least one shot was fired during the struggle and then the officer fired more shots before leaving the car, police said.
But a witness to the shooting interviewed on local media has said that Brown had been putting his hands up to surrender when he was killed.
"There were many, many witnesses who have talked to family members and they paint a very different picture than police witnesses," said Benjamin Crump, a lawyer for the Brown family. Crump also represented the family of Trayvon Martin, an unarmed black teen killed in Florida by a neighbourhood watch volunteer in 2012.
The "hands up" gesture has been frequently seen at protests over the shooting. More than 100 protesters in front of the St Louis County Courthouse in nearby Clayton on Tuesday morning chanted "hands up, don't shoot".