The verdict came after the Seminole County jury of six women deliberated a total of about 15 hours over two days following a five-week trial, the Orlando Sentinel reported. The panel could have found him guilty of second-degree murder or manslaughter.
"You have no further business with this court," Circuit Judge Debra Nelson told Zimmerman moments after the verdict was read.
The Sentinel said Zimmerman, who maintained he shot Trayvon in self-defense during a nighttime encounter while the teen walked through a gated community in Sanford in February 2012 as he walked back to his father's home after a trip to a convenience store, hugged members of his family after the verdict was read at 10 p.m. EDT. George's wife Shellie smiled and cried.
Trayvon's parents, Sybrina Fulton and Tracy Martin, were not in the courtroom when the verdict was read, the newspaper said.
Special prosecutor Angela Corey, after the verdict was delivered, said prosecutors had promised to seek justice for the slain 17-year-old.
"To the living we owe respect. To the dead, we owe the truth," she said. "We have shown respect to the living and we believe we have brought out the truth on behalf of Trayvon Martin."
Law enforcement officers were posted outside the courthouse where about 100 people peacefully chanted "No justice, no peace!" The New York Times reported.
The Rev. Al Sharpton called Zimmerman's acquittal "a slap in the face to the American people" but added "it is only the first round in the pursuit of justice."
"We intend to ask the Department of Justice to move forward as they did in the Rodney King case and we will closely monitor the civil case against Mr. Zimmerman," the civil rights activist said in a statement. "I will convene an emergency call with preachers tonight to discuss next steps."
The Miami Herald reported Martin family attorney Benjamin Crump said "all the evidence was there to convict" Zimmerman, now 29.
"This family is heartbroken that the killer of their son is not going to be held accountable," Crump said. "It makes no sense that in 2013 you can follow and shoot an unarmed teenager walking home with nothing other than candy and a drink, and go free."
Earlier in the evening, the jurors had asked the judge to clarify her instructions for the charge of manslaughter.
"May we please have clarification on the instructions regarding manslaughter?" the jurors' written question to Nelson asked.
The Sentinel reported that after the attorneys in the case and Nelson discussed the matter the judge read aloud the following statement given the jury:
"The court cannot engage in general discussions but may be able to address a specific question regarding clarification of the instructions regarding manslaughter. If you have a specific question please submit."
Meanwhile, law enforcement officers interceded when a verbal confrontation erupted in the Seminole County courthouse Saturday afternoon. The Sentinel said a man, who identified himself as Jack Scott, a Zimmerman supporter from Winter Springs, walked up to a group of Martin supporters and shouted "go get your welfare checks" and "go get your crack." Scott and a man from that group got into a verbal altercation, prompting officers to step in, the newspaper said.
"There was a verbal disagreement between two individuals in the assembly zone and deputies simply pulled them aside individually to ask them to be respectful of one another," Seminole County Sheriff's Office spokeswoman Heather Smith said. "They both agreed, they are both still there, and there was never any physical contact between the two individuals."
The jury had deliberated all day Saturday after mulling the case for 3 1/2 hours Friday after the defense ended its closing arguments.
Dozens of people also had gathered outside the courthouse Friday. Afterward, some of them assembled peacefully at a "free speech zone" near a fountain outside the building.
Five miles away, about 30 people met in the predominately black community of Goldsboro to discuss the case.
Police have prepared for possible violence, but Friday's crowds were mostly calm, the newspaper said.
A leader of the International People's Democratic Uhuru Movement showed up at the courthouse with a megaphone, but complied with deputies' requests to stop using it.
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