French investigating police in protective clothing prepare to enter the Thalys high-speed train where shots were fired to collect clues in Arras, France, August 21, 2015. [Photo/Agencies]

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. 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, 'pencer, 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 US 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.