Amy and her husband Joe were sitting quietly on the Amsterdam-Paris Thalys train Friday evening when the window behind her was shattered by a bullet, showering her with glass.
Another passenger, Damien, was reading a magazine when he heard what he described as a "click-click-click".
"I thought it was a toy," the still-shocked 35-year-old told AFP.
What followed was fifteen seconds of confusion and chaos.
A gunman armed with a Kalashnikov had opened fire on the high-speed train, carrying more than 550 passengers -- but, almost before bystanders had time to react, he had been overpowered by several passengers including off-duty American servicemen.
Two people were wounded in the struggle, including, according to the Pentagon, a member of the US military, though it was not clear if they were the same people who had subdued the gunman.
Ten minutes later the train stopped at Arras, where police arrested the shooter, described by French investigators as a 26-year-old from Morocco or of Moroccan origin also armed with an automatic pistol and a box cutter.
In Arras, stunned passengers waited to speak to police as the Red Cross distributed bottled water.
"The man stopped between two carriages, fired and it made a click-click-click sound, not at all like in the films," Damien told AFP.
"Then the man, who was bare-chested, returned to carriage 12 and someone in a green T-shirt, with a shaved head, saw him and jumped on him and pinned him to the ground."
The entire scene, he said, "did not last more than fifteen seconds".
'Blood was everywhere'
Christina Cathleen Coons, an American tourist, said she had been in carriage 12 when the shots rang out. "I heard gunshots, probably two, and a guy collapsed," she recounted.
"There was a woman in the background, perhaps 40 years old, with her husband -- I saw the glass over her break because of the shot," the 28-year-old New Yorker said.
"A guy fell on the ground and blood was everywhere, apparently he was hit in the neck."
Pressed to the floor of the carriage, she quickly began snapping pictures on her smartphone -- images that swiftly went around the world.
"I thought there was going to be a shoot-out on the train," she said.
Laurent, a 40-year-old from Paris who was in the next carriage, said Thalys staff rushed into his car.
"A lady came into our train shouting 'he was shot, he is losing blood, is there a doctor?'" he said.
Laurent knew first aid -- but he hesitated, he said, unsure if the gunman was still on the loose.
Once it emerged that the shooter had been subdued, he went to help.
"I saw a person on the ground, another person had made a tourniquet around his neck, I saw him move," he said.
Another person lay restrained on the ground, he said, referring to the shooter.
A woman nearby was panicking, he said, wondering why the train continued to move and help did not come. "There was a lot of panic."
Amy, the American tourist who had been sitting beneath the window when it was shattered by the bullet, was being comforted by her husband Joe.
"I saw the glass fall over my wife's shoulders," Joe said.
Describing the men who tackled the shooter, he said one was wearing an LA Lakers T-shirt and the other a football jersey.
"I'm proud they responded quickly, preventing a disaster," he said, adding that there were "no more than six or seven people" in the first-class carriage.
"We express our great gratitude to these gentlemen, the two men who stopped the shooter," Amy added.