PARIS -- The woman was crumpled on the floor of a mangled Mercedes, unconscious and struggling to breathe. The French doctor had no idea who she was and just focused on trying to save her.
Twenty-five years later, Dr. Frederic Mailliez is still marked by what happened in the Alma Tunnel in Paris on Aug. 31, 1997 - and the realization that he was one of the last people to see Princess Diana alive.
"I realize my name will always be attached to this tragic night," Mailliez, who was on his way home from a party when he came across the car crash, told The Associated Press. "I feel a little bit responsible for her last moments."
As Britain and Diana's admirers worldwide mark a quarter-century since her death, Mailliez recounted the aftermath of the crash.
That night, Mailliez was driving into the tunnel when he spotted a smoking Mercedes nearly split in two.
"I walked toward the wreckage. I opened the door, and I looked inside," he said.
What he saw: "Four people, two of them were apparently dead, no reaction, no breathing, and the two others, on the right side, were living but in severe condition. The front passenger was screaming, he was breathing. He could wait a few minutes. And the female passenger, the young lady, was on her knees on the floor of the Mercedes, she had her head down. She had difficulty to breathe. She needed quick assistance."
He ran to his car to call emergency services and grab a respiratory bag.
"She was unconscious," he said. "Thanks to my respiratory bag (...) she regained a little bit more energy, but she couldn't say anything."
The doctor would later find out the news - along with the rest of the world - that the woman he treated was Diana, Britain's national treasure adored by millions.
"I know it's surprising, but I didn't recognize Princess Diana," he said. "I was in the car on the rear seat giving assistance. I realized she was very beautiful, but my attention was so focused on what I had to do to save her life, I didn't have time to think, who was this woman."
"Someone behind me told me the victims spoke English, so I began to speak English, saying I was a doctor and I called the ambulance," he said. "I tried to comfort her."
MORE: William and Harry to reunite at Diana statue unveiling
As he worked, he noticed the flash of camera bulbs, of paparazzi gathered to document the scene. A British inquest found Diana's chauffeur, Henri Paul, was drunk and driving at a high speed to elude pursuing photographers.
Mailliez said he had "no reproach" toward the photographers' actions after the crash. "They didn't hamper me having access to the victims. ... I didn't ask them for help, but they didn't interfere with my job."
Firefighters quickly came, and Diana was taken to a Paris hospital, where she died a few hours later. Her companion Dodi Fayed and the driver also died.
"It was a massive shock to learn that she was Princess Diana, and that she died," Mailliez said. Then self-doubt set in. "Did I do everything I could to save her? Did I do correctly my job?" he asked himself. "I checked with my medical professors and I checked with police investigators," he said, and they agreed he did all he could.
WATCH: Remembering Princess Diana
The anniversary is stirring up those memories again, but they also come back "each time I drive through the Alma Tunnel," he said.
As Mailliez spoke, standing atop the tunnel, cars rushed in and out past the pillar where she crashed, now bearing a stencil drawing of Diana's face.
The Flame of Liberty monument nearby has become a memorial site attracting Diana fans of all generations and nationalities. She has become a timeless figure of emancipation and a fashion icon even for those born after her death.
Irinia Ouahvi, a 16-year-old Parisian visiting the flame, said she knows Diana through TikTok videos and through her mother.
"Even with her style she was a feminist. She challenged royal etiquette, wearing cyclist shorts and casual pants," Ouahvi said.
Francine Rose, a Dutch 16-year-old who stopped by Diana's memorial while on a biking trip in Paris, discovered her story thanks to "Spencer," a recent film starring Kristen Stewart.
"She is an inspiration because she was evolving in the strict household, the royal family, and just wanted to be free," Rose said.
Nicolas Garriga and Jeffrey Schaeffer contributed to this report.