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Tucked away in the footnotes of history, she is referred to in police records as Witness #43.

And for five decades, most people had no clue what Mary Ellen Ford saw on April 4, 1968.

At the time, a 21-year-old Ford was a waitress and cook at the famed Lorraine Motel in Memphis, Tennessee, where the Rev. Martin Luther King Jr. would stay to take part in the civil rights protests sweeping the South.

Ford opened up on "Today" for the first time in decades — on the eve of the 50th anniversary of King's assassination — to describe what she witnessed and how her life was forever changed. Her own brother only learned five years ago that she was at the motel when a sniper's bullet claimed King's life, altering the course of a movement.

Ford is etched into the pages of history via a famous photo after the shooting. She is seen in white, her right arm folded across her waist as other workers wait anxiously for an ambulance to arrive.

"I never even talked about it, because I do — I get so emotional," she told NBC News' Craig Melvin.

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Ford said that, before King was shot, she would catch glimpses of him as he came and went from Room 306 of the motel. At one point, she was tasked with delivering hamburgers to him and other civil rights leaders who used the motel room as a de facto headquarters.

"When I took the tray in, I set it on the table," Ford recalled. "And like I say, he was laying on the bed ... smoking a cigarette, because he smoked."

At 6:01 p.m. on April 4, Ford was cooking in the kitchen when she heard a loud burst ring out. She thought people were shooting off firecrackers. She was mistaken.

"We all ran outside to see what was going on and he was laying on the balcony," Ford said of King. "And I'm standing there. I'm just dumbfounded, you know? Just shocked."

"Like, what just happened, you know? This don't happen here. And — this not OK," she added, wiping away tears.

A lone gunman, later identified as James Earl Ray, shot King as he stood on the motel's second-floor balcony. The moment was a blur, and she could hear people screaming out: "They shot Dr. King! They shot Dr. King!"

Lorraine Motel employee Mary Ellen Ford is highlighted in a section of the photo taken after the assassination. Courtesy of National Civil Rights Museum

In the aftermath, as news spread of the attack, Ford said phone calls began pouring into the motel.

"Even the payphone on the outside, they were calling on that," she said. "'Did Dr. King get shot? Did Dr. King get shot?'"

King would later die at the hospital. Ray escaped and was captured two months later in the United Kingdom. He died in prison in 1998.

Today, the Lorraine Motel houses the National Civil Rights Museum. Ford, who eventually moved to Lansing, Michigan, and raised a family, doesn't like to speak publicly about that terrifying day. She does not like to think of herself as Witness #43.

Rather, her favorite memory, she said, is of the people who would come to the motel each time King stayed there, waiting to see the civil rights leader emerge from his room — and knowing they were witnessing a luminary who would change the country.

"Standing, sitting on the brick wall, waiting to get a glimpse of Dr. King," she said of the onlookers. "Just to see Dr. King."