Story highlights Watch captain says he shot a teen in self-defense, authorities say

If the boy had been the shooter, he would have been arrested, his dad says

The shooter has not been charged; the teenager was unarmed

The attorney for the slain boy's family says the Sanford, Florida, police "passed the buck"

The family of a 17-year-old unarmed Florida boy gunned down last month is outraged that the shooter remains free.

"It's surprising. It's shocking," said Tracy Martin, father of Trayvon, shot dead in Sanford. "It lets me know that justice is just not being served here. All we want is justice for our son. We're not asking for anything out of the ordinary."

Trayvon Martin was returning from a convenience store to the home of his father's fiancee in a gated community around sunset on February 26. A neighborhood watch captain, George Zimmerman, 28, saw the teen and called 911 to report a suspicious man, authorities said.

The 911 dispatcher told Zimmerman not to confront the person, but by the time police arrived, Trayvon Martin lay dead with a gunshot wound in the chest, said Sanford Police Chief Bill Lee. The teenager was carrying a small amount of cash, some candy and an iced tea.

Zimmerman told police he shot the teen in self-defense, authorities said, and he remains free as the state attorney's office investigates the case. Police said they have not charged Zimmerman because there are no grounds to disprove his story of what happened.

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The shooting has sparked outrage in the community, with some accusing Zimmerman, who is white, of profiling the black teen.

The boy's parents and the family attorney were interviewed Friday by CNN's Soledad O'Brien.

Tracy Martin told CNN that if Trayvon pulled the trigger, "he would have been arrested on the spot."

Benjamin Crump, the Martin family's attorney, said Zimmerman should have been arrested.

"He can make that self-defense argument. But that's in court with the judge and the jury after he's been arrested," he said.

Zimmerman's freedom "doesn't pass the common-sense test," Crump said. He said the police department "passed the buck" to the state attorney's office. He said there have been "other instances like this" involving the department.

"And now they are doing an investigation. So more nights go by where these parents go to bed knowing that their son is in a grave and the man who killed their son is sleeping his own bed," Crump said.

Trayvon was a normal, growing boy with a big appetite, his parents said.

"He loved playing football. He loved watching football. He loved basketball," said his mother, Sybrina Fulton. "He loved to eat everything in your house."

Tracy Martin describes the anguish of losing a son.

"It's sad as a father to have to bury your child. As a parent, you never want to imagine about burying your kids. And for me to have to bury my son is just sad," he said.

The Martin family has sought to make the 911 tapes available, but State Attorney Norm Wolfinger said Tuesday the calls will not be made public until the investigation is complete. A gunshot can be heard on the 911 calls that night, police said.

"Trayvon Martin and his family, interested persons, and the public-at-large are entitled to no less than a thorough, deliberate and just review of the information provided, along with any other evidence that may or may not be developed in the course of the review process," Wolfinger's office said in a statement. "We intend to honor that commitment."

Numerous CNN attempts to contact Zimmerman were unsuccessful, and it is unclear whether he has retained an attorney.

"The evidence and testimony we have so far does not establish that Mr. Zimmerman did not act in self-defense. We don't have anything to dispute his claim of self-defense, at this point, with the evidence and testimony that we have," said Lee, the police chief.

Lee said the 911 directions asking Zimmerman not to confront the teenager are not mandatory instructions.

"That is a call taker making a recommendation to him. He's not under a legal obligation to do that, so that is not something we can charge him with," he said. "But it would have been a good outcome ... if Trayvon Martin and George Zimmerman never came in contact with one another."

In a letter sent to U.S. Attorney General Eric Holder, the National Association for the Advancement of Colored People expressed doubt in the Sanford Police Department and asked the Justice Department to review the case.

"The NAACP has no confidence that, absent federal oversight, the Sanford Police Department will devote the necessary degree of care to its investigation," the letter said. "We therefore call upon you to detail personnel to Sanford immediately to review the facts, ensure that the Sanford Police Department conducts an impartial, thorough and prompt investigation of the circumstances involving the death of this unarmed teen, and ensure that the responsible person is held accountable if a crime was committed."