Thirty-eight years after he was assassinated on a motel balcony, photographs, recordings and police files that describe the death of Martin Luther King Jr. have been placed on the internet.

On yesterday's anniversary of Dr King's death, the Shelby County Register’s office in Memphis, Tennessee, made available hours of tapes, including hurried police calls from the scene of the crime, hundreds of photographs and thousands of pages of files and transcripts of the trial of James Earl Ray, the man found guilty of the shooting.

Dr King was shot in the jaw while he spoke to supporters from his balcony outside Room 306 of the Lorraine Motel in downtown Memphis in the early evening of April 4, 1968. He was in the city, and under police surveillance, trying to lead a peaceful protest of sanitation workers. He died an hour later.

The assassination was witnessed by dozens of people, including a clutch of police officers and firefighters who were watching Dr King from the locker room of Fire Station No 2, across the road from the motel.

Recordings of their first radio calls to the Memphis emergency despatcher were released yesterday. Through the scramble of voices come the words: "a shooting has occurred.... I'm at the Lorraine in the car... it has been verified that Reverend King has been shot... it has been confirmed that Reverend King has been shot."

The subsequent hour of calls, edited to 18 minutes on the website, show the rapid pace of events that later became the US Government's case against Ray, who first admitted shooting Dr King before recanting and insisting for the rest of his life, with the support of the King family, that he was framed for the crime.

Within moments, police officers can be heard saying that the fatal shot was fired from a run-down flophouse across the road from the motel: "The Reverend King has been shot from a brick building, it's a brick building directly east from the Lorraine Motel."

Then the description of a suspect and a make of car that became crucial evidence in the case against Earl Ray: "Got a description? A young white male, well dressed, a young white male, well dressed, running south from 424 South Main."

Officers are then told to look out for a "late model white Mustang". Minutes later a "bundle" containing a rifle was found outside a record shop.

Ray, an armed robber on the run after escaping from prison in Missouri in April 1967, was arrested in London two months after the shooting. He was held at Heathrow travelling under the name "Ramon George Sneyd" and his fingerprints were found to match those on the rifle found outside the Memphis record shop.

Ray confessed to the assassination, saying he stood in the bathtub of the communal bathroom in the flophouse to take the shot, and was sentenced to serve 99 years in prison. He died in jail in 1998 after four investigations, including a review by the Department of Justice, failed to find evidence to support a theory that Dr King was shot on the orders of a Memphis bar-owner.

Tom Leatherwood, the Register of Shelby County, said that the files surrounding the death of Dr King, including photographs of the flophouse, of Earl Ray and the "bundle", had been kept for years in the county archives before being moved to the register last year.

"I have younger children ranging from 5 to 13," he said. "And they are just not aware of the cost of the civil rights movement. Martin Luther King gave his life for civil rights and so many people in America today just take that for granted."

"These files and the despatch tape, especially, are a real slice of history. When I heard it for the first time it was very chilling to me. It can make it very real for a new generation."

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