Trayvon Martin died on a rainy February evening in Sanford, Fla., as he walked back to the home of his father's girlfriend after a stroll to a nearby 7-Eleven to buy a snack for his little brother.
His killer, a Latino man named George Zimmerman, claims he was acting in self-defence and said the 17-year-old boy's hoodie made him look suspicious.
Zimmerman, 28, hasn't been charged with a crime, with Florida law enforcement officials pointing to the state's so-called Stand Your Ground law that allows people to shoot if they fear they're in danger. Nonetheless Zimmerman was told not to engage when he called 911 about Martin.
The Sanford police chief stepped down on Thursday after the police commission voted 3-2 that it had no confidence in his handling of the case.
Saying he was "keenly aware of the emotions associated with the tragic death of a child," Bill Lee said he was stepping aside temporarily because he'd become a "distraction" to a community in turmoil.
Martin's parents believe race was a factor in their son's Feb. 26 death. The U.S. Justice Department has launched a civil rights probe into the case; department officials were slated to meet with Martin's family on Thursday in Florida.
The shooting has stirred ever-simmering racial tensions in the United States amid reports that Zimmerman had a history of targeting young black men as he patrolled his neighbourhood.
He's heard saying "these assholes, they always get away" in a 911 call released earlier this week.
"Because black life is cheap, a young person of colour can do everything 'right' and still end up dead," Chauncey DeVega, a Chicago blogger and black activist, wrote on Salon.com this week.
"What does this mean for blackness, when a century or more after the end of slavery, and decades after the end of lynch law, that your guilt is still assumed?"
Protests calling for charges against Zimmerman have been held for weeks and are ongoing, including one at a Sanford church on Thursday night with civil rights activist Al Sharpton in attendance. Thousands showed up for a similar rally in New York City on Wednesday, including Martin's parents.
More than a million people have signed a petition on the Change.org website urging law enforcement officials to arrest and charge Zimmerman. The petition was gaining steam on Thursday, with more than 1,000 people signing it per minute, according to Change.org officials.
But in a statement earlier this week, Lee said his officers were "prohibited from making an arrest based on the facts and circumstances they had at the time." He added they had physical evidence that supported Zimmerman's self-defence claim.
"The Sanford Police Department has conducted a complete and fair investigation of this incident," said Lee, adding it's now up to prosecutors to determine whether to lay charges.
Sanford police commissioner Velma Williams, the only black member of the commission, told reporters she'd spent 15 years trying to ease racial tensions between blacks and whites in the community about a half hour south of Orlando.
"And now this. It's a national embarrassment," she said after voting against Lee's handling of the case.
Members of Sanford's black community say the police force's gentle treatment of Zimmerman is typical, pointing to similar incidents in the past. Black teen Travares McGill was shot dead by white security guards in 2005 — one of them was the son of a Sanford police veteran, the other was a volunteer for the force. The case was later dismissed by a judge.
In 2010, the beating of a black homeless man by a white teenager was captured on videotape. Police didn't arrest a suspect for seven weeks; he was the son of a Sanford police lieutenant.
Martin's death has also renewed a national debate about the right to bear arms, a hallowed, constitutionally enshrined civil liberty in the United States. Stand Your Ground laws, which exist in at least 21 American states, allow citizens to use deadly force against someone else if they fear for their life.
The law also deems no one has to retreat if they feel threatened or attacked.
Arthur Hayhoe, executive director of the Florida Coalition to Stop Gun Violence, has been railing against the legislation for years.
"You want to know how you can kill somebody legally in Florida?" he said. "Make sure you have no witnesses, hunt the person down and then say you feared for your life."
The Florida law was put in place in 2005, after a man shot and killed a burglar allegedly trying to break into his RV following a deadly hurricane. The man was never charged.
Martin's shooting has prompted the NAACP to ask Sanford residents to share their stories of discrimination and abuse at the hands of the community's police force. The information will be handed over to the Justice Department.
Some African-American men have already come forward to discuss what it entails, even in 2012, to be a black man in the United States.
Corey Dade, a digital journalist at NPR, wrote a poignant piece about "the talk" on the news outlet's website.
"For other boys coming of age, parents may end 'the talk' after a lecture about sex, drugs, alcohol or Internet porn," he wrote. "The rite for black boys often is more rigorous: We're also drilled on a set of rules designed to protect us against suspicions too often associated with the colour of our skin."
James C. Morant of the Baltimore Sun also weighed in.
"'He was suspicious looking.' 'He seemed threatening.' These are the codes assigned to African-American males, whether young or old, rich or poor, educated or uneducated, successful or not so successful," he wrote in a column on Thursday.
"I thought that the enlightened, 'post-racial' era would have dispensed with these views, but that is clearly not the case."