Two of the victims were in critical condition, according to a statement from the office of President Francois Hollande.

"Everything is being done to shed light on this tragedy," Hollande said on Twitter.

The French actor Jean-Hugues Anglade also reportedly injured his hand when he broke a glass to pull an alarm.

The 26-year-old suspect was arrested after the train stopped in Arras, 115 miles north of Paris, Interior Ministry spokesman Pierre-Henri Brandet said on French television BFM.

The Prefect of Pas-de-Calais, Fabienne Buccio, said the suspect should be regarded as a terrorist, according to La Voix du Nord.

The French newspaper La Voix du Nord reports that the gunman was overpowered by passengers, including the two Marines. The newspaper said the pair heard the man loading the automatic weapon in a bathroom on the train and overpowered the gunman before he could open fire inside the main train cars. Earlier reports said that one of the soldiers was British.

Another American, Anthony Sadler, helped subdue the alleged gunman, according to the Associated Press. He was the traveling companion of the two Marines, who he identified as Spencer Stone and Alek Skarlatos. Stone was the injured American, Sadler said.

He described the chaos of the scene, from hearing a gunshot to seeing a man enter the train car with an automatic rifle.

"As he was cocking it to shoot it, Alek just yells, `Spencer, go!` And Spencer runs down the aisle," Sadler told AP. "Spencer makes first contact, he tackles the guy, Alek wrestles the gun away from him, and the gunman pulls out a box cutter and slices Spencer a few times. And the three of us beat him until he was unconscious."

French Interior Minister Bernard Cazeneuve, who arrived on the scene late Friday, denounced the "barbaric act." He praised the "two deserving passengers" for their "great bravery and composure," the newspaper said.

The newspaper, quoting a prosecutor, reported that one of the soldiers was injured by a gunshot and the other by a knife.

A Pentagon spokeswoman confirmed that one U.S. military member was injured in the incident. The Pentagon described the injury as "not life-threatening."

The suspect was identified as a Moroccan, said Sliman Hamzi, an official with police union Alliance, said on French television i-Tele. He was known to French intelligence services, Agence France-Press reports, quoting unidentified police sources.

Christophe Piednoel, a spokesman for national railway operator SNCF, said the suspect was carrying both an automatic rifle and a knife.

President Obama, updated on the attack Friday evening, "expressed his profound gratitude for the courage and quick thinking of several passengers, including U.S. service members, who selflessly subdued the attacker," a White House official said. "It is clear that their heroic actions may have prevented a far worse tragedy."

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