Sixty-one years ago, the bodies of three murdered civil rights workers were found in the Deep South. The public's response to the FBI's Mississippi Burning investigation provided the impetus for enacting landmark civil rights legislation across the US.

When Julian Bond, the co-founder of the Student Nonviolent Coordinating Committee (SNCC) sat down to talk to the BBC in July 1964, it was just over two weeks since the disappearance of young civil rights workers in Mississippi had begun dominating the US news headlines.

Warning: The following video contains discriminatory language, used in a historical context, which some may find offensive.

The three men had been part of "Freedom Summer" – a three-month initiative launched by SNCC, the Congress of Racial Equality (Core) and other civil rights organisations, to encourage as many black people as possible in Mississippi to register to vote. In 1961, despite roughly 45% of Mississippi's population being black, less than 7% were registered to vote. Freedom Summer's goal was to tackle the laws and fear tactics that were being used to disenfranchise the state's black voters.

Hundreds of volunteers, many of them college students from northern states, travelled down to the South to help establish Freedom Schools. These centres, as well as teaching classes in black history and civil rights, helped potential voters pass the literacy tests and fill in the forms the state required, so that they could cast their votes. Twenty-four-year-old Nancy Stearns was one of the young volunteers who had travelled from the North to participate in the project. "I believe that this situation in the US must be changed," she told the BBC in 1964. "As it is now, it's an extremely unjust society. It doesn't change by itself, it only changes through some sort of force, some sort of agitation, if you will. And I want to put my life in and be part of this attempt at change."

But the Freedom Summer initiative had sparked intense and often violent resistance from white supremacists and local authorities in Mississippi. The campaigners, and the black voters who attended the lessons, faced constant intimidation and violence. Black churches were routinely torched, and activists threatened and assaulted.

On 21 June 1964, the three young Core staffers – James Chaney, a 21-year-old black native of Mississippi, and his two white colleagues, Jewish New Yorkers 20-year-old Andrew Goodman and 24-year-old Michael Schwerner – travelled to investigate the firebombing of Mount Zion Methodist Church in Neshoba County. The black church had been targeted by the Ku Klux Klan (KKK) because it acted as an organising centre for the Freedom Summer campaign.

After examining the church's charred remains and interviewing members of the congregation, who had suffered savage beatings at the hands of the Klansmen, the three men left the site to return to the Core office. On their way, the station wagon they were driving was stopped by Deputy Sheriff Cecil Price for an alleged traffic violation. Chaney was the driver, and yet Price arrested all three men and took them to the Neshoba County jail in Philadelphia, Mississippi. They were not allowed to call anyone on the phone or, initially, to pay the fine.

Because of the febrile atmosphere at the time, if Core staff did not return when they were expected, it was procedure to ring around local police stations and hospitals. But despite Core's phone records showing the police station was called at around 17:30, Minnie Herring, the jailer's wife, denied that anyone inquired about the three men. At around 22:30, the three civil rights workers were finally allowed to pay the fine, and were released from custody. Price told them to leave the county. They were not heard from again.

Bond believed that the disappearance was designed to spread fear among the people working on Freedom Summer. And while it did cause a couple of volunteers to have second thoughts, he said that for many of the activists it served to underscore the importance of what they were trying to achieve: getting black people registered to vote. "They are determined they are going to continue doing what they are doing… and the disappearance of those three just shows them exactly what they are up against," Bond told the BBC in July 1964. "That there are people in this country who will do anything to stop democracy from becoming a reality."

Unlike previous victims of racial violence, the missing men prompted a huge response from the US Justice Department. Attorney General Robert Kennedy classified the case as a kidnapping........

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