Hosie Miller, a black farmer and Baptist deacon in Newton, Ga., was fatally shot in 1965 after he reportedly told a white neighbor he wanted to settle a dispute in court. The FBI closed the case in 2011, saying agents believe the neighbor was responsible, but he was dead and could not be prosecuted.

O'Neal Moore, a Washington Parish, La., police officer, was killed in 1965, just a year after being named the area's first black officer. A reported white supremacist was arrested but charges were dropped. More than five years have passed since the FBI reopened Moore's case, and it remains open. "I don't have any answers," Moore's widow, Maevella Moore, says. "I want to know who."

Louis Allen was shot in his driveway in Liberty, Miss., in 1964. The FBI said an investigating officer in the case was "potentially involved" in the slaying. But no arrests have been made, and the case remains open.

Charles Moore and Henry Dee, of Franklin County, Miss. Ku Klux Klan members kidnapped the teens in 1964, chained them to a Jeep engine block and pushed them into the Mississippi River, the FBI said. James Ford Seale and Charles Edwards were arrested, but the charges were dropped. After reopening the case, authorities granted immunity to Edwards — who agents said did not participate in the killings. He testified against Seale, who was convicted of kidnapping and conspiracy and sentenced to three life terms.

Jimmie Lee Jackson was shot in 1965 after a civil rights protest in Marion, Ala. State trooper James Bonard Fowler said his gun discharged after Jackson struck his hand, but witnesses reported seeing Fowler deliberately shoot Jackson, the FBI said. In 2007, with FBI assistance, local authorities charged Fowler with murder. He pleaded guilty to manslaughter in 2010 at age 77 and received a six-month prison sentence.