Protests were held Sunday after a US jury found George Zimmerman not guilty of murdering unarmed black teen Trayvon Martin, in a racially charged trial that transfixed the country.
The trial aroused strong passions among those who believed that Zimmerman -- a volunteer neighborhood watchman whose father is white and whose mother is Peruvian -- racially profiled and stalked Martin, and those convinced he acted in self-defense.
Spontaneous protests broke out overnight in US cities including San Francisco, Philadelphia, Chicago, Washington and Atlanta, with larger organized gatherings planned later Sunday.
In Oakland, California, protesters smashed windows and spray painted cars, but most overnight demonstrations were peaceful -- and closely watched by police.
Zimmerman, 29, had been accused of pursuing Martin, 17, through a gated community in Sanford, Florida, and shooting him during an altercation on the rainy night of February 26, 2012.
Florida police initially declined to press charges against Zimmerman, sparking mass protests in several US cities. He was eventually arrested in April 2012 and charged with second-degree murder and manslaughter.
The specter of the deadly April 1992 riots in Los Angeles, which broke out after a similarly racially-charged case, still lingers among law enforcement officials.
Fearing violence after the verdict, activists and community leaders appealed for calm. Police were out in force in Sanford, and the crowd of several hundred outside the courthouse was loud at times, but peaceful.
"Obviously, we are ecstatic with the results. George Zimmerman was never guilty of anything except protecting himself in self-defense," said his lead attorney Mark O'Mara after the verdict.
Defense attorney Don West was even more blunt, calling the prosecution of Zimmerman "disgraceful."
Defense lawyers insisted Zimmerman feared for his life after Martin attacked him, pinned him to the ground and started slamming his head against the pavement.
Zimmerman is the only living witness to how the fight began.
"Even though I am broken-hearted my faith is unshattered I WILL ALWAYS LOVE MY BABY TRAY," Martin's father Tracy wrote on Twitter.
Both he and Martin's mother Sybrina Fulton gave thanks for the outpouring of support they had received over the past year.
Zimmerman's older brother Robert also took to Twitter: "Message from Dad: 'Our whole family is relieved.' Today... I'm proud to be an American. God Bless America! Thank you for your prayers!" he wrote.
The Martin family's attorney Benjamin Crump declined to say whether they would file a civil lawsuit against Zimmerman, but said "they are going to certainly look at that as an option."
"They deeply want a sense of justice. They deeply don't want their son's death to be in vain," he told ABC News's "This Week."
"They are still in disbelief about his death and now they're in disbelief about this verdict... They're in church this morning, praying and turning to God, a higher authority, to make sense of it all."
Community leaders called for calm after the verdict.
"There will be protests, but they must be carried out with dignity and discipline and let no act discredit the legacy of Trayvon Martin on the appeal of his family," civil rights leader Reverend Jesse Jackson said Sunday on CNN.
Reverend Al Sharpton, an activist television host, said on Facebook that the acquittal was "a slap in the face to the American people," and that he was convening "an emergency call with preachers (to) discuss next steps."
The NAACP, the largest US civil rights group, urged supporters to sign a letter asking Attorney General Eric Holder to file civil rights charges against Zimmerman.
"The most fundamental of civil rights - the right to life - was violated the night George Zimmerman stalked and then took the life of Trayvon Martin," read the NAACP letter.
"We ask that the Department of Justice file civil rights charges against Mr Zimmerman for this egregious violation."
Prosecutors argued that Zimmerman, who pursued Martin against the advice of a police dispatcher, instigated the confrontation.
The all-female jury had to reach a unanimous verdict to convict or acquit, and deliberated for more than 16 hours on the case after closing arguments Friday.
Zimmerman faced possible life in prison if convicted of second-degree murder. The jury was also instructed to consider an alternative charge of manslaughter, which carries a sentence of up to 30 years.
A leftist coalition that helped organize demonstrations against the Iraq war said it would hold marches Sunday in eight US cities, and more protests are expected in the coming days.