PARIS » A gunman opened fire on a high-speed train traveling from Amsterdam to Paris on Friday, wounding two people before American passengers subdued him, according to officials and one of the Americans involved.

French Interior Minister Bernard Cazeneuve, speaking in Arras in northern France where the suspect was detained, said one of the Americans was hospitalized with serious wounds.

Two of the Americans were in the military, according to traveling companion Anthony Sadler, senior at Sacramento State University. He told The Associated Press that the injured American was Spencer Stone of Sacramento, and the other was Alek Skarlatos of Roseburg, Oregon.

"We heard a gunshot, and we heard glass breaking behind us, and saw a train employee sprint past us down the aisle," Sadler said from France. They saw a gunman entering the train car with an automatic rifle, he said.

"As he was cocking it to shoot it, Alek just yells, ‘Spencer, go!’ And Spencer runs down the aisle," Sadler said. "Spencer makes first contact, he tackles the guy, Alek wrestles 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."

"The gunman never said a word," he added.

Sadler said Stone helped another passenger who had been wounded in the throat and losing blood.

Philippe Lorthiois, an official with the Alliance police union, said on French television i-Tele that the two Americans were soldiers. In Washington, the Pentagon said it "can only confirm that one U.S. military member was injured in the incident. The injury is not life-threatening."

The White House issued a statement saying that President Barack Obama was briefed on the shooting, and said: "While the investigation into the attack is in its early stages, it is clear that their heroic actions may have prevented a far worse tragedy."

Contrary to early reports, Lorthiois said the attacker did not fire his automatic weapon but wounded one man with a handgun and the other with a blade of some kind.

The suspect is a 26-year-old Moroccan, according to Sliman Hamzi, an official with the police union Alliance, who spoke on i-Tele.

Investigators from France’s special anti-terror police are leading the investigation, a spokeswoman for the Paris prosecutor’s office said.

"As always where an act that could be terrorist in nature is involved, the greatest care and the greatest precision will be used," Cazeneuve said.

Cazeneuve said the two Americans "were particularly courageous and showed great bravery in very difficult circumstances," and that "without their sangfroid we could have been confronted with a terrible drama."

A third person, French actor Jean-Hugues Anglade, suffered a minor injury while activating the train’s emergency alarm, Lorthiois said.

Passenger Christina Cathleen Coons of New York described the drama in car 12 of the train in an interview with Ouest France newspaper.

"I heard shots, most likely two, and a guy collapsed," she is quoted as saying.

Coons, identified as a 28-year-old vacationing in Europe, said a window broke above one woman’s head. "A guy fell to the floor and had blood everywhere," she is quoted as saying.

She described lying on the floor herself and taking photos with her phone.

"I thought there would be a shootout in the train," the newspaper quotes her as saying. Then, "people came to take care of him."

The attack took place at 1545 GMT while the Thalys train was passing through Belgium, according to a statement from the office of French President Francois Hollande.

Hollande said he had spoken with Belgian Prime Minister Charles Michel, and the two leaders pledged to cooperate closely on the investigation.

A young woman said on i-Tele that she was in the carriage next to the one that the gunman struck.

"I wouldn’t call it a fusillade, because even in the next wagon we didn’t hear any shots," said Margaux, who declined to give her last name. She said passengers remained "relatively calm," and some showed no concern until police boarded the train.

Europe’s major rail stations, such as Paris’ Gare du Nord and Brussels’ Gare du Midi, are patrolled by soldiers armed with rifles, but passengers can board most high-speed trains without passing through metal detectors or having their bags searched.

One exception is the Eurostar between Paris and London. Passengers on those trains must pass through a metal detector and have their bags scanned as well.

Thalys is owned by the French and Belgian railways and operates high-speed trains serving Paris, Brussels, Amsterdam and Cologne, Germany.

French authorities have been on heightened alert since Islamic extremist attacks in January left 20 people dead, including the three attackers.

Siek reported from New York. Associated Press writers Lolita C. Baldor in Washington and Nadine Achoui-Lesage in Arras contributed to this report.