The parents of an unarmed African American teenager who was shot dead in Sanford, Florida, last month are formally calling on the FBI to take over the investigation as they have lost confidence in the local police and prosecutors.
Trayvon Martin, 17, was fatally shot by a Hispanic neighbourhood watch volunteer George Zimmerman, who has admitted the killing, claiming self-defence.
But three weeks later, Zimmerman, 28, has not been charged, sparking accusations of racial stereotyping and poor investigation.
Martin, from Miami, was visiting his father in Sanford. On February 26, he was watching the NBA all-star game at a house in a gated community called the Retreat at Twin Lakes. At half time, he left the house to the convenience store to get some candy and a drink. On his way back, he was spotted by Zimmerman, who was patrolling the area in his car and who called 911 to report what he described as a "real suspicious guy."
The release of the 911 tapes over the weekend, which the family say proves Zimmerman was not acting in self-defence, provoked a further storm of outrage, with rallies and petitions demanding Zimmerman's arrest.
Students rallied on Monday in front of the Seminole County criminal courts building in Sanford, where prosecutors will review the case and decide whether to file charges against Zimmerman, and on the campus of Florida A&M University in Tallahassee.
Attorney Benjamin Crump, who is representing Martin's family, told reporters that 17-year-old Martin's parents both broke down and cried as they listened to the 911 recordings.
"They are completely devastated. They are in unbelievable grief," Crump told the Huffington Post.
The 911 tapes, eight recording of the events of February 26 were made public on Friday after the family sued to have them released.
They reveal how Zimmerman pursued Martin, against warnings from the operator. Later, 911 calls from neighbours reveal how there were calls for help before a single shot rang out.
"Hey, we've had some break-ins in my neighbourhood and there's a real suspicious guy," Zimmerman tells police before giving the address. "This guy looks like he's up to no good or he's on drugs or something."
Zimmerman then tries to explain where he is. "Now he's coming towards me. He's got his hand in his waistband. And he's a black male … Something's wrong with him. Yup, he's coming to check me out. He's got something in his hands. I don't know what his deal is … These assholes, they always get away."
Zimmerman then said: "Shit, he's running."
"Are you following him?" the operator asked. Zimmerman replied: "Yep."
"OK, we don't need you to do that," the operator warned.
But by the time police arrived, Martin lay dead with a gunshot wound in the chest.
"Hurry, please … there's someone screaming outside," a neighbour whispers on another 911 recording. "There's a gunshot. Hurry up."
In another call, a woman begs the dispatchers to send help, saying someone is "screaming and hollering" for help.
Martin's parents, Tracy Martin and Sybrina Fulton, accused Sanford police of not investigating their son's killing properly, and criticised them for not arresting Zimmerman, according to CBS News. They say the police department hasn't arrested Zimmerman because he is white and their son was black.
Police initially told Martin's father that they didn't charge him because Zimmerman was a criminal justice student with a " squeaky clean" record, according to the Huffington Post.
But Crump said public records show that Zimmerman was arrested in July 2005 in Orange County on charges of resisting arrest with violence and battery on a law enforcement officer. The charges appear to have been dropped.
"They just lied to the family," Crump said. "They just couldn't see why [Zimmerman] would do anything wrong or be violent. But not only do you know the guy killed this kid, because he admitted to it, you knew that he has a propensity for violence because of his past record."
Reports of the case suggest that Zimmerman was a vigilante with a false sense of authority. Police records show Zimmerman had called 911 a total of 46 times between 1 January this year and the day he killed Martin, according to Mother Jones.
Zimmerman told police he fired his 9mm pistol in self-defence, and he has a lawful concealed weapons permit.
Martin was carrying was his cell phone, a can of iced tea and a bag of Skittles.