PARIS (AP) — French authorities formally opened a terrorism investigation Tuesday after a thwarted attack on a high-speed train last week, saying the suspected gunman had watched a jihadi video onboard minutes before the violence.

The decision to open an investigation was based on the actions of 26-year-old Moroccan suspect Ayoub El-Khazzani on the train Friday night and information from other European authorities about his travels and apparent links to radical Islam, prosecutor Francois Molins told reporters.

Molins said El-Khazzani notably watched the online video on his phone minutes before he walked through the Amsterdam-to-Paris train carrying an assault rifle and other weapons. Authorities say they found his phone in a bag left in the train.

The gunman was tackled and tied up by three American friends and a British businessman. Another man who tried to stop him — a French-American named Mark Moogalian — remained hospitalized Tuesday with a gunshot wound.

Now that the formal investigation is opened, investigating magistrates are expected to file numerous preliminary charges against El-Khazzani, including multiple attempted murders in connection with terrorism, possession of weapons in connection with terrorism, and participation in a terrorist conspiracy.

According to French law, authorities must file preliminary charges against the suspect by Tuesday night or seek a special extension to his temporary custody.

The next step will be determining where his weapons came from, how he financed them and whether he had any accomplices, Molins said.

El-Khazzani was found to have an AKM assault rifle with 270 rounds of ammunition, a 9mm handgun, a box-cutter and a bottle of gasoline, the prosecutor said.

Prosecutors also found a small explosive warhead hidden in the glass box containing the hammer used to break train windows in case of an emergency. They didn’t elaborate.

The suspect had travelled through several European countries and had been repeatedly incarcerated in Spain and flagged for surveillance in France, Molins said.

After five to seven months in 2014 in France, El-Khazzani lived successively in Brussels, Cologne, Vienna, and then again in Cologne and Brussels — but the prosecutor gave no indication of dates.

French surveillance helped authorities spot the suspect on a flight May 10 from Berlin to Istanbul, then on a return flight from Antakya, Turkey, to Tirana, Albania, via Istanbul, Molins said. The suspect, however, denied going to Turkey. He may have tried to go to Syria.

Under questioning, El-Khazzani said he had no terrorism plans and had found a bag of weapons the night before in a Brussels park and planned to use them to rob passengers, according to Molins. But his explanation grew less and less lucid, the prosecutor said, and the suspect eventually stopped speaking to French investigators at all.

El-Khazzani boarded the train on Friday at a Brussels station.

One reason investigators suspect a planned attack was that El-Khazzani, who claimed to be homeless and living in a Brussels park, took a first-class ticket and refused to take an earlier train even though there were seats available.

In Brussels, investigators searched two buildings where the gunman may have stayed in the Molenbeek-Saint-Jean neighborhood, the Federal Prosecutor’s Office said in a statement Tuesday. No one was detained or taken in for questioning, although investigators seized “some objects” for further examination.

Two people were injured in Friday’s attack: U.S. Airman 1st Class Spencer Stone and Moogalian, who is hospitalized in northern France with a bullet wound.

U.S. military authorities in Germany say Stone is doing well at an American military hospital where he is being treated. Landstuhl Regional Medical Center spokesman Chuck Roberts said Stone arrived at the facility in southern Germany on Monday and seemed in good spirits, smiling and shaking hands with leaders of the U.S. military hospital.

He says Stone is being treated for a laceration to his thumb, for which a full recovery is expected with ongoing therapy, as well as a “non-critical” eye injury and other minor wounds.

It’s not yet clear when Stone will be transferred back to the United States.

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Lorne Cook in Brussels, David Rising in Berlin, and Angela Charlton in Paris, contributed to this report.