Sanford Police Chief Bill Lee's announcement came less than a day after city commissioners gave him a "no confidence" vote, and after a couple of weeks of protests and uproar on social media websites. Lee has said the evidence in the case supported George Zimmerman's claim that the Feb. 26 shooting of 17-year-old Trayvon Martin was self-defense.
"I do this in the hopes of restoring some semblance of calm to a city which has been in turmoil for several weeks," Lee said.
Martin was returning from a trip to a convenience store when Zimmerman started following him, telling police dispatchers he looked suspicious. At some point, the two got into a fight and Zimmerman pulled out his gun.
Zimmerman told police Martin attacked him after he had given up on chasing the teenager and was returning to his sport utility vehicle.
The shooting ignited racial tensions in this Orlando suburb. Civil rights groups have held rallies in Florida and New York, saying the shooting was unjustified.
The police chief continued Thursday to stand behind his agency's investigation.
"As a former homicide investigator, a career law enforcement officer and a father, I am keenly aware of the emotions associated with this tragic death of a child. I'm also aware that my role as a leader of this agency has become a distraction from the investigation," Lee said.
It wasn't immediately how long the police chief would step aside.
The Justice Department and FBI have opened a civil rights investigation, and the local prosecutor has convened a grand jury April 10 to determine whether to charge Zimmerman.
Some people believed Lee should step down for good.
"If they wanted to defuse a potential powder keg, he needed to resign," said pastor Eugene Walton, 58, who was born and raised in Sanford. "His inaction speaks loudly to the black community."
News of the police chief's decision to step aside spread quickly among the 1,000 protesters who had shown up more than two hours before the start of the rally Thursday. They chanted "The chief is gone. Zimmerman is next."
Some carried signs that said: "100 years of lynching, justifiable homicide. Same thing." Others sold T-shirts that said: "Arrest Zimmerman."
"It's the norm around here, where anything involving black culture, they want to wipe their hands of it," said Shella Moore, who is black and grew up in Sanford.