Florida's governor has appointed a new prosecutor to oversee the investigation into last month's shooting death of an unarmed black teenager.

Gov. Rick Scott late Thursday appointed Angela B. Corey to oversee the investigation into the death of Trayvon Martin.

She is the prosecutor for the Jacksonville area. Scott said this came after the local prosecutor for the central Florida county where the shooting happened, Norman Wolfinger, volunteered to recuse himself.

Martin's parents have complained that the 28-year-old shooter, George Zimmerman, has not been charged after he claimed self-defence.

Scott also appointed a task force led by Lt. Gov. Jennifer Carroll to hold hearings about the Feb. 26 shooting and make recommendations for changing state laws and procedures.

Florida chief in case of slain teen steps aside

Sanford police Chief Bill Lee, who was bitterly criticized for not arresting Zimmerman in the shooting death, also announced he was temporarily stepping down on Thursday, saying he had become a distraction to the investigation.

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.

George Zimmerman is seen in police mug shot provided by Florida's Orange County Jail, via The Mimai Herald, from a 2005 arrest. Zimmerman is the neighborhood watch captain who shot unarmed teenager Trayvon Martin, 17. (Associated Press/Orange County Jail/Miami Herald)

Zimmerman told police 17-year-old Trayvon 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. Late Wednesday, city commissioners gave the police chief a "no confidence" vote.

"I must temporarily remove myself from the position as police chief for the city of Sanford. 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. "It is my hope that the investigation will move forward swiftly and appropriately through the justice system and that a final determination in this case is reached."

Role as chief a 'distraction' for investigation

The police chief has said authorities were prohibited from making an arrest based on the facts and circumstances they had at the time of the shooting. He said he continued 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 clear how long the police chief would step aside. Martin's parents said that wasn't enough, and that Zimmerman should be taken into custody.

"We want an arrest, we want a conviction and we want him sentenced for the murder of my son," Martin's father, Tracy, said to fiery crowd of about 1,000 supporters in downtown Sanford.

Some people believed the police chief 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."

'Zimmerman is next,' crowd chants

News of the police chief's decision to step aside spread quickly among the protesters, many of whom showed up more than two hours before the start of the rally. 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 read: "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.

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.

Before the rally, Martin's parents met with the local U.S. attorney, the deputy assistant attorney general for civil rights in Washington and the head of the FBI's Tampa office to discuss the investigation.

"We listened carefully to the concerns of the family and their representatives," Special Agent Dave Couvertier, an FBI spokesman, said in a statement. "We continue to extend our deepest condolences to Trayvon's family for their loss."