April 4, 1968, The civil rights leader was in Memphis to support a sanitation workers’ strike and was on his way to dinner when a bullet struck him in the jaw and severed his spinal cord. King, pronounced dead after his arrival at a Memphis hospital. He was 39 years old.

In the months before his assassination, Martin Luther King became increasingly concerned with the problem of economic inequality in America. He organized a Poor People’s Campaign to focus on the issue, including an interracial poor people’s marchon Washington, and in March 1968 traveled to Memphis in support of poorly treated African-American sanitation workers. On March 28, a workers’ protest march led by King ended in violence and the death of an African-American teenager. King left the city but vowed to return in early April to lead another demonstration.

On April 3, back in Memphis, King gave his last sermon, saying, “We’ve got some difficult days ahead. But it really doesn’t matter with me now, because I’ve been to the mountaintop…And He’s allowed me to go up to the mountain. And I’ve looked over, and I’ve seen the Promised Land. I may not get there with you. But I want you to know tonight that we, as a people, will get to the promised land.”

One day after speaking those words, Dr. King was shot and killed by a sniper. As word of the assassination spread, riots broke out in cities all across the United States and National Guard troops were deployed in Memphis and Washington, D.C. On April 9, King was laid to rest in his hometown of Atlanta, Georgia. Tens of thousands of people lined the streets to pay tribute to King’s casket as it passed by in a wooden farm cart drawn by two mules.

The evening of King’s murder, a Remington .30-06 hunting rifle was found on the sidewalk beside a rooming house one block from the Lorraine Motel. During the next several weeks, the rifle, eyewitness reports, and fingerprints on the weapon all implicated a single suspect: escaped convict James Earl Ray. A two-bit criminal, Ray escaped a Missouri prison in April 1967 while serving a sentence for a holdup. In May 1968, a massive manhunt for Ray began. The FBI eventually determined that he had obtained a Canadian passport under a false identity, which at the time was relatively easy.

On June 8, Scotland Yard investigators arrested Ray at a London airport. He was trying to fly to Belgium, with the eventual goal, he later admitted, of reaching Rhodesia. Rhodesia, now called Zimbabwe, was at the time ruled by an oppressive and internationally condemned white minority government. Extradited to the United States, Ray stood before a Memphis judge in March 1969 and pleaded guilty to King’s murder in order to avoid the electric chair. He was sentenced to 99 years in prison.

Three days later, he attempted to withdraw his guilty plea, claiming he was innocent of King’s assassination and had been set up as a patsy in a larger conspiracy. He claimed that in 1967, a mysterious man named “Raoul” had approached him and recruited him into a gun running enterprise. On April 4, 1968, he said, he realized that he was to be the fall guy for the King assassination and fled to Canada. Ray’s motion was denied, as were his dozens of other requests for a trial during the next 29 years.

During the 1990s, the widow and children of Martin Luther King Jr. spoke publicly in support of Ray and his claims, calling him innocent and speculating about an assassination conspiracy involving the U.S. government and military. U.S. authorities were, in conspiracists’ minds, implicated circumstantially. FBI Director J. Edgar Hoover obsessed over King, who he thought was under communist influence. For the last six years of his life, King underwent constant wiretapping and harassment by the FBI. Before his death, Dr. King was also monitored by U.S. military intelligence, which may have been asked to watch King after he publicly denounced the Vietnam War in 1967. Furthermore, by calling for radical economic reforms in 1968, including guaranteed annual incomes for all, King was making few new friends in the Cold War-era U.S. government.

Over the years, the assassination has been reexamined by the House Select Committee on Assassinations, the Shelby County, Tennessee, district attorney’s office, and three times by the U.S. Justice Department. The investigations all ended with the same conclusion: James Earl Ray killed Martin Luther King. The House committee acknowledged that a low-level conspiracy might have existed, involving one or more accomplices to Ray, but uncovered no evidence to definitively prove this theory. In addition to the mountain of evidence against him–such as his fingerprints on the murder weapon and his admitted presence at the rooming house on April 4–Ray had a definite motive in assassinating King: hatred. According to his family and friends, he was an outspoken racist who informed them of his intent to kill Dr. Martin Luther King, Jr. He died in 1998.