ARRAS, France - A heavily armed man with ties to radical Islam who was known in three European countries as potentially dangerous escaped the radar when he boarded a high-speed train -- but not the courage of three American passengers who took him down.

Two U.S. servicemen, one in the Air Force, another who recently served in Afghanistan in the National Guard, and their friend who is a student, tackled and disarmed the gunman with the help of a Briton, winning trans-Atlantic kudos.

Ayoub El-Khazzani, 26, was being questioned by French counter-terrorism police who confirmed through fingerprints their suspicions that he was the man on their radar since February 2014. Interior Minister Bernard Cazeneuve said Spanish authorities had advised French intelligence about him because he belongs to the "radical Islamist movement."

As the Amsterdam to Paris train passed through Belgium, a French citizen trying to use the toilet encountered and tried to subdue the gunman, who had a Kalashnikov strapped across his shoulder, Interior Minister Bernard Cazeneuve said, adding him to the heroes list.

Bullets sounded and the Americans moved in. The train, in Belgium, was rerouted to Arras in northern France, the nearest station, where El-Khazzani was arrested.

A duel French-American citizen with a bullet wound was helicoptered to a hospital in nearby Lille and the Air Force man, Spencer Stone, was taken to another Lille hospital for a hand injury. He was released at day's end. Police in Arras questioned his two friends. A heavily guarded cortege was seen arriving Saturday night at the U.S. ambassador's residence in Paris, apparently escorting the three.

Stone, of Carmichael, California, Anthony Sadler, a senior at Sacramento State University, and Alek Skarlatos, a National Guardsman from Roseburg, Oregon, were traveling together when they heard a gunshot and breaking glass. Sadler told The Associated Press thaat they saw a train employee sprint down the aisle followed by a man with an automatic rifle.

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"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 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."

Throughout the brief but terrifying episode, Sadler said, "The gunman never said a word."

But with the weapons he carried, "he was there to do business," Skarlatos said in an interview shown on French television.

Sadler's father, Tony Sadler, said he received a call from his son after the drama.

"He leaves here a young man on an excursion to broaden his world view and to have fun with his buddies and he comes back a France's national hero," Tony Sadler told Sacramento TV station KCR.

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French officials said the suspect had lived in the southern Spanish city of Algeciras, frequenting a mosque which is under surveillance there. He was transferred Saturday morning to anti-terror police headquarters outside Paris and can be held for up to 96 hours.

An official linked to Spain's anti-terrorism unit said the suspect lived in Spain until 2014, then moved to France, traveled to Syria, and then returned to France. He spoke on condition of anonymity because he was not authorized to be identified by name.

The French official close to the investigation said the French signal "sounded" on May 10 in Berlin, where El-Khazzani was flying to Turkey. The French transmitted this information to Spain, which advised on May 21 that he no longer lived there but in Belgium. The French then advised Belgium, according to the official close to the investigation.

"We don't know if he went on to Syria, if he returned," the official said.

The Belgian federal prosecutor's office has also opened an investigation because the suspect boarded the train in Brussels, said spokesman Eric Van der Sypt. Belgium also announced it was imposing stricter security on trains.

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French authorities are on heightened alert after Islamic extremist attacks in January left 20 people dead, including the three gunmen. In June, a lone attacker claiming allegiance to Islamic radicals beheaded his employer and set off an explosion at an American-owned factory in France, raising concerns about other scattered, hard-to-predict attacks.

Chris Norman, the British businessman who helped the Americans subdue the gunman, said he was working on his computer when he heard a shot and glass breaking and saw a train worker running.

Norman was the fourth to jump into the fray, grabbing the gunman's right arm and tying it with his tie.

"He had a Kalashnikov, he had a magazine full .... My thought was, OK, probably I'm going to die anyway. So, let's go," Norman told reporters. "I'd rather die being active."

President Barack Obama telephoned Stone, Skarlatos and Sadler to commend and congratulate them, the White House said.

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Skarlatos, 22, had returned from a deployment in Afghanistan in July, and Stone is stationed in the Azores, according to Skarlatos' step-mother Karen Skarlatos.

French actor Jean-Hugues Anglade injured his finger, cutting it to the bone while activating the train's emergency alarm, he told Paris Match magazine. Anglade said he had felt certain he, his two children and family were doomed.