Read TIME’s Original 1997 Special Report on Princess Diana’s Death

There was little sound for the first two minutes after the crash except for the hoarse wail of the mangled car’s horn. The noise emanated weakly from both ends of the tunnel on Paris’ Place de l’Alma—from the east end, which the black Mercedes with the silver trim had entered just moments before, moving at least twice the 35 m.p.h. the local traffic laws allow; and from the west end, where the narrow tunnel opened onto a spectacular view of the left bank of the Seine. On the still busy streets above—where the lights of the Eiffel Tower had yet to be shut off for the night—the muffled sound of one car horn might not even be noticed.

But seconds earlier there had been a tremendous noise. Tom Richardson and Joanna Luz, visitors from San Diego, were walking near the mouth of the tunnel when they saw the car enter, feverishly pursued by a swarm of motorcycles and scooters, then heard what sounded to them like an explosion. Just inside the 660-ft. tunnel, the car struck the concrete divider that separates the eastbound lanes from the westbound and then apparently cartwheeled, rolling over a full 360° and spinning around nearly 180°.

When Richardson and Luz ran into the tunnel, they saw the car facing back in the direction from which it had come, its roof crushed, its windshield smashed and its air bags deployed. The chauffeur, killed instantly, slumped over the wheel, the weight of his body pressing the dead car’s horn. In front of the wreck, a paparazzo—the last Diana paparazzo—raised his camera and began to snap. “When I ran into the tunnel, he was already there,” Richardson said. “I could see that his equipment was far too sophisticated for a tourist.”

It took only minutes for the Paris police to arrive, cordoning off the area with red- and-white crime-scene tape and leaving the lights of their cruisers flashing as they rushed into the tunnel. The officers broke into two groups: one headed straight for the wrecked car, the other fanned out to nab the photographers believed to have caused the accident. There were more than seven paparazzi thought to have been involved in the high-speed pursuit, and at least five were still in the tunnel. All were quickly arrested and led out in manacles. When they emerged, the crowd that had begun to gather jeered, and one cuffed cameraman was even set upon and beaten before police could hustle him away.

Back in the tunnel, the scene was a grim one. Almost the instant the second group of officers reached the car, it was clear that the chauffeur and Al Fayed, both sitting on the vehicle’s left side, were beyond help. Diana and her bodyguard, however, both on the right, appeared to be clinging to life.

“We knew it was somebody messed up bad,” says Michael Walker, another American tourist whose taxi passed the wreckage, where he stopped to gawk and take pictures. “It was a bad accident. The car was crushed and tilted up against the wall.” The taxi driver thought he saw a blond-haired woman sitting in the backseat of the car, gasping, crying.

As the onlookers watched, the rescue team cut through the buckled roof and doors of the Mercedes, removed the two survivors and rushed them by ambulance to a public hospital, the Pitie-Salpetriere, one of the best in the city. On the way, paramedics examined the wounded princess and found her condition grave. She was suffering from extensive chest injuries, a massive wound to the left lung and numerous broken bones. Her blood pressure barely registered on the rescue team’s instruments.

When the ambulance reached the hospital, the emergency-room physicians found that Diana was alive—just barely—but that the injuries had caused extensive internal bleeding. For more than two hours they struggled to stabilize her, eventually opening her chest and applying direct massage to her heart. But the loss of blood and the system-wide trauma proved too much. At 4 a.m. Paris time, after two hours of massaging Diana’s unbeating heart, doctors declared the princess dead.

Read the rest of the special report here, in the TIME Vault