The parents of a black teenager fatally shot by a white neighborhood watch volunteer called on the FBI Friday to take over the investigation, saying they no longer trust the local police department.

Meanwhile, the shooter's father is defending his son, saying he is not a racist and did not provoke the altercation that led to the shooting.

The parents of Trayvon Martin told an Orlando press conference they no longer trust the Sanford Police Department. Their 17-year-old son was fatally shot last month as he returned to a Sanford home during a visit from Miami.

Tracy Martin and Sybrina Fulton accused Sanford police of botching the investigation and criticized them for not arresting 28-year-old George Zimmerman, who says he shot Trayvon Martin in self-defense. Martin was not armed. They say the police department hasn't arrested Zimmerman because he is white and their son was black.

"Do we really believe that if Trayvon Martin would have pulled the trigger, he would not be arrested?" said Benjamin Crump, their attorney. "This is obviously a cover-up, and we need a sweeping overhaul of the Sanford Police Department."

Sanford police Sgt. David Morgenstern said the department stands by its investigation but welcomes help from any outside agency. FBI agent David Couvertier said the agency has been in contact with Sanford police and is monitoring the case. U.S. Rep. Corrine Brown, D-Fla. and Sanford Mayor Jeff Triplett said Friday they supported federal involvement.

"We want the oversight," Triplett said. "We want the review of it."

Several residents who spoke to The Associated Press on Friday said they think there would have been an arrest already if the shooter had been black and the deceased had been white. But they also said whites as well as blacks in this city of 53,000 residents tend to agree that an injustice had been done with no one arrested, and that local perception of the case doesn't break down along a racial divide. The city is 57 percent white and 30 percent black. It has a median household income of almost $42,000.

"To me, I don't think it's even a race issue, other than for the people involved," Ladonna Williams, 38, who is black, said as she shopped at the Seminole Towne Center shopping mall, more than a mile the shooting took place. "It's just about ... to be able to take somebody's life in 2012 and not even go to jail for it, that is just sad. No matter, for any color. Not just black or white. Any color."

Shopper Joanne Johnson said she thought Sanford police just wanted the matter to drop, saying it's a blot on a community that has undergone a renaissance in the past decade. New art galleries, antique shops, bistros and cafes have opened up in downtown Sanford in recent years, giving vitality to a community that often has been overshadowed by nearby Orlando.

"I think they want to make it go away," said Johnson, who is white. "It makes the community look bad."

The shooting took place about two miles from the downtown restaurants and galleries in a gated community of townhomes nestled behind an elementary school and a city park. A white cross covered in flowers was at the gate's entrance Friday.

"I think most people here are in agreement about it, that there's a large possibility that it's a racist act," said Sam Boylston, 19, who is white and a salesman at Tuned Up Music Center in downtown. "You would hope something like this would bring people together to seek justice."

Meanwhile, Zimmerman's father delivered a letter to the Orlando Sentinel on Thursday saying the way his son is being depicted in the media is cruel and misleading. He also says his son has received death threats and moved out of his home. George Zimmerman is Hispanic and grew up in a multiracial family, the statement says.

"He would be the last to discriminate for any reason whatsoever ...," the letter says. "The media portrayal of George as a racist could not be further from the truth."

No one disputes that Zimmerman shot Martin on the night of Feb. 26. Martin, who was visiting from Miami, was walking back to the home of his father's fiancée after going to the store to buy candy for his little brother and an iced tea for himself. It was raining, and Martin was walking with the hood of his jacket pulled over his head.

Zimmerman called 911 from his sports utility vehicle, saying he had spotted a suspicious person walking in the multiracial neighborhood. Officials say the dispatcher told him to stay in his SUV and an officer would be there momentarily. But Zimmerman for unknown reasons got out. He and Martin fought, according to witnesses. At some point Zimmerman pulled a gun and shot Martin, who died at the scene. Zimmerman told Sanford police he acted in self-defense. He has not been arrested or charged.

The 911 tape has not been released, but officials said it would be made public later Friday.

Sanford investigators say they have turned over their evidence to prosecutors for them to decide whether Zimmerman should be charged.

The letter Zimmerman's father gave the Sentinel says George Zimmerman didn't get out of the SUV to confront Martin.

"At no time did George follow or confront Mr. Martin. When the true details of the event become public, and I hope that will be soon, everyone should be outraged by the treatment of George Zimmerman in the media," the letter said.

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(Photo: Orlando Sentinel/MCT/Landov)