BUTT-WHIPPIN:

The three Americans were on a weeks-long tour through Europe, enjoying time together after Alek Skarlatos, 22, a National Guardsman from Roseburg, Ore., had been deployed to Afghanistan. Stone, an Air Force serviceman, is based in the Azores. Anthony Sadler is a student at Sacramento State University, according to their families.

The shooter emerged from a train bathroom with what the Americans believed to be an AK-47, according to family members whom they spoke with shortly after the incident. The men saw a train employee run down the aisle of the train, followed by the attacker.

"Alek said that they were about 30 feet away and ran for him, and Spencer, the friend, got him down, and Alek took the gun and knocked him a few times with the butt of the gun," said Skarlatos's stepmother, Karen Skarlatos, by telephone. "Then the shooter grabbed for a handgun, which they took away from him as well, and then he grabbed for a cutter, a box cutter or a knife or something."

After the attacker was overpowered, a fourth man, British national Chris Norman, helped tie him up.

In the struggle, Stone was injured by the knife, she said. But the men managed to hogtie the assailant and subdue him, she said. A shaky cellphone video of the outcome showed the subdued man, shirtless and in white pants, lying with his front on the floor of the train car, his legs tied up in the air.

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