Hundreds of people are gathering at the local police department in Sanford, Fla. to protest the killing of 17-year-old Trayvon Martin by a neighborhood watch volunteer, and they're calling for the arrest of George Zimmerman.

Demonstrators walked through Sanford's streets, carrying signs and wearing T-shirts with Martin's image.

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The 17-year-old was shot by Zimmerman as he walked back to his father's fiancée home in a gated community in Sanford. Zimmerman said the teen looked suspicious and that he shot him in self-defense after he and Martin fought.

Martin's family doubts Zimmerman's story and has been joined by civil rights leaders and protesters around the country in calling for his arrest.

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