They want mob justice for an someone they accuse of being a vigilante. From Fox News:
"We cannot allow a precedent when a man can just kill one of us ... and then walk out with the murder weapon," said civil rights leader Al Sharpton, flanked by Martin's parents and a stage full of supporters at a rally in Sanford on Thursday night. "We don't want good enough. We want George Zimmerman in court with handcuffs behind his back."
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Martin's parents said the police chief's action wasn't enough, and that Zimmerman should be taken into custody.
"We want an arrest, we want a conviction and we want him sentenced for the murder of my son," Martin's father, Tracy, said to the fiery crowd of protesters at Fort Mellon Park.