PARIS — Looking awed by the sumptuous gilded surroundings of the United States ambassador’s residence here, the three young American men who thwarted an attack on a Paris-bound express train appeared at a news conference on Sunday, brushing aside suggestions that they were heroes.

Airman First Class Spencer Stone and Alek Skarlatos, who are in the armed forces, and Anthony Sadler, a friend of theirs, sat side by side, soberly recounting the experience. It could have been merely a particularly lively finish to an otherwise pleasant night out, in their telling: no heroics, and nothing dramatic about it.

Mr. Stone, his arm in a sling and one eye bruised from the struggle with the young Moroccan suspect who is now in police custody, rapidly recounted what happened.

“I got him in a chokehold,” he said. “He kept taking out more weapons. He took out a box cutter.” He was cut by the box cutter and had hand surgery afterward.

Asked what had motivated him to tackle the heavily armed man, Mr. Stone said simply: “To survive.”

There was no mistaking the man’s determination, Mr. Stone said. “He seemed like he was ready to fight to the end, and so were we,” he told reporters.