Tracy Martin, father of slain Florida teen Trayvon Martin, joins a protest called "A Million Hoodies March" to demand justice for his son's death, in New York's Union Square March 21, 2012. [Photo/Agencies]

SANFORD, Florida - A local police chief and a Florida state prosecutor overseeing the case of an unarmed black teenager shot dead by a neighborhood watch captain stepped aside on Thursday following withering criticism and national outrage that police have declined to arrest the shooter.

Sanford Police Chief Bill Lee's resignation - which he called "temporary" - failed to appease civil rights and community leaders who are calling for the arrest of watch captain George Zimmerman, 28, who shot 17-year-old Trayvon Martin and claimed self-defense.

Lee was under mounting pressure for days and suffered a a "no confidence" vote from the city commission on Wednesday. The shakeup at the state level was more surprising as Gov. Rick Scott replaced Tallahassee's lead investigator and formed a task force to review Florida's controversial "Stand Your Ground" law.

Police have said this law, which allows people to use deadly force when they perceive danger in any public place, prevented them from arresting Zimmerman, a white Hispanic who has disappeared from public view.

Zimmerman's father has said his son has been unfairly vilified. He called him a friend of minorities whose true nature was being distorted by national calls for his arrest and allegations that he pursued Martin just because he was black.

Coupled with at least two prior cases that stoked black anger toward the police, the response to the Martin episode had grown so intense Lee said he had no option but to step aside as "my involvement in the matter is overshadowing the process."

Similarly, State Attorney Norman Wolfinger said he was stepping down "with the intent of toning down the rhetoric."

Criticism of the investigation came on top of a history of racial tension in Sanford, a town of about 50,000 just north of Orlando.

In 2011, a previous Sanford police chief was forced out of the job after a white police officer's son was captured on video sucker-punching a black homeless man outside a bar.

Sanford police did not immediately arrest the officer's son, Justin Collison. 

But after video of the attack surfaced on local TV and the Internet and provoked an outcry from Sanford civil rights leaders, Collison was charged weeks later with aggravated battery and disorderly conduct. He eventually pleaded guilty to a misdemeanor charge.

The incident came five years after two white private security guards with ties to the police department shot and killed a black teenager.

The guards - one the son of a Sanford police officer and the other a department volunteer - said they opened fire in self-defense, claiming the teenager attempted to run them over. Evidence showed the teenager died from a gunshot in the back. The cases were eventually dismissed due to lack of evidence.

The Martin case generated mostly local interest in the days following the Feb. 26 shooting but has steadily drawn the national spotlight, which has only grown in recent days since the state of Florida and U.S. Justice Department announced their own investigations and the city commission voted 3-2 in favor of a "no confidence" motion against Lee on Wednesday night.

A mostly black crowd that city officials estimated at 10,000 gathered in a Sanford park to protest against the handling of the Martin case and what black leaders have called a pattern of racial discrimination in Sanford and elsewhere in a country that nonetheless has elected a black president.

New York-based civil rights leader Al Sharpton, whose TV show on MSNBC raised the profile of the Sanford shooting, headlined a series of speakers calling for justice.

Cathey Law, 46, a human-resource manager in the crowd, said the shooting had resonated in her family.

"I have a young adult son. In our black community, we have to have that conversation about driving while black and walking while black," Law said. "I hope his (Martin's) murder is not in vain and things change."

Earlier, Sanford City Commissioner Patty Mahany said relations between the police and blacks were poor well before Lee took charge of the department 10 months ago.

Rather than any single scandal, she said the trouble amounted to "smaller, more insidious things, but that were still part of that whole culture that were present at that time in the police department."

"The African American community here in Sanford feels very strongly that they were treated differently. It seems to be the very same complaints you hear on a national level: the reasons for police stops, things that were said to them at police stops, the way arrests were handled and investigations were handled," she said. 

Sanford City Manager Norton Bonaparte, who is black, told Reuters he understands the outrage over the killing and acknowledges the case "does conjure up a negative image of our city and it is disturbing."

"There is the race issue," he said. "That's indisputable."