BROWNSVILLE, Tenn. (AP) - A man historians believe to be the first NAACP member killed for daring to speak up for civil rights was remembered at a memorial service in Brownsville, Tennessee, where he was slain 75 years ago.

More than 500 people attended the service at a high school gymnasium on Saturday to honor Elbert Williams, who was killed by unknown assailants on June 20, 1940, amid a drive to register black voters.

Williams was taken from his home by a group of men led by a police officer, and his body was found later in the Hatchie River. His slaying was never solved.

NAACP President Cornell William Brooks spoke at the service. He called Williams a martyr and said "no sacrifice should be forgotten."

Following the memorial service, a historical marker was unveiled in Williams' honor.

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