A Florida police chief criticised over the investigation into the shooting of an unarmed black teenager has announced he will temporarily step down.
Bill Lee had been censured by officials in Sanford, an Orlando suburb, over the death of Trayvon Martin.
A mass rally led by civil rights leader Reverend Al Sharpton will be held later to demand justice for the 17-year-old.
Neighbourhood watchman George Zimmerman, 28, was not charged for shooting the teenager.
He said he was defending himself because Mr Martin had attacked him. In Florida, a law known as "stand your ground" can prevent criminal or civil prosecution when deadly force is used in self-defence.
Mr Lee explained his decision at a news conference.
"It is apparent that my involvement in this matter is overshadowing the process," he said.
"Therefore I have come to the decision that I must temporarily remove myself."
"I do this in the hope of restoring some semblance of calm to the city, which has been in turmoil for several weeks," he added.
'Flogging police chief'
Mr Lee's decision to stand aside comes a day after city commissioners in Sanford issued a vote of no-confidence in him.
hey voted 3-2 to censure the police chief, who has held his position for just 10 months.
"I take no pleasure in a public flogging of our police chief," Commissioner Mark McCarty said, according to the Orlando Sentinel. "But he really should turn in his resignation."
Mr Martin's parents have met federal officials reviewing police conduct.
Nearly one million people have signed online petitions calling for justice.
Mr Sharpton tweeted that he would still attend the rally despite the death of his mother, who passed away on Wednesday.
"My MOM would have wanted me to," he said.
In anticipation of large numbers of protesters, the rally venue was moved from a 400-seat church to Fort Mellon Park in Sanford.
On Wednesday, Mr Martin's parents addressed a mass rally in New York to call for the arrest of Mr Zimmerman.
His father, Tracy Martin, told that so-called Million Hoodie March: "My son did not deserve to die," and said police had racially profiled his son.
Although Mr Martin was killed in late February, the publication of 911 emergency calls and sworn testimony from a friend have fuelled debate over whether the shooting was truly a case of self-defence.
A Florida grand jury is considering whether there is enough evidence to file charges, and the US justice department has launched a probe into the local police investigation.
In a statement Sanford City Manager Norton Bonaparte called the death of Mr Martin a "tragic situation".
But he emphasised that officers of the Sanford police department were "prohibited from making an arrest based on the facts and circumstances they had at the time".Mr Martin was unarmed and on his way home af
ter buying sweets from a local shop, his parents say.
Transcripts of phone calls released by police indicate that Mr Zimmerman called the police after seeing Mr Martin, describing him as "real suspicious".
The recordings suggest the police dispatcher told Mr Zimmerman not to pursue the teenager.
Mr Zimmerman has said he shot Mr Martin to defend himself after the teenager attacked him.
Details of the confrontation remain unclear.
Florida's self-defence law, enacted in 2005 and known as "stand your ground", gives people scope to use deadly force rather than retreat during a fight.