PARIS — An Islamic State operative went on trial on November 16 in Paris on terror charges for swaggering bare-chested through a train in 2015 with an arsenal of weapons and shooting one passenger. He was brought down by three American vacationers, including Greek-American Alek Skarlatos, in an electrifying capture that Clint Eastwood turned into a Hollywood thriller.

Skarlatos recently ran as the Republican candidate for election to the U.S. House to represent Oregon's 4th Congressional District, but lost in the tight race to the incumbent Democrat Peter DeFazio.

The scene five years ago on the fast train from Amsterdam to Paris is the focus of the month-long trial of Ayoub El Khazzani, with testimony expected from the two U.S. servicemen and their friend, who have been hailed as heroes.

Their lawyer, Thibault de Montbrial, said at the courthouse Monday that their "very brave intervention" had thwarted a “slaughter.”

Lawyer of Islamic State operative Ayoub El Khazzaniin, Sarah Mauger-Poliak, speaks to media on the opening day of the Thalys attack trial, at the Paris courthouse, Monday, Nov. 16, 2020. (AP Photo/Thibault Camus)

“This terror attack could have killed up to 300 people based on the number of ammunition that was found on the terrorist and in his bag,” he said.

With El Khazzani in court and watched by security officers, the trial opening was largely taken up with procedural issues including whether Eastwood’s presence is needed. That question was not immediately resolved. The actor-director has so far not responded to a summons. Eastwood turned the Aug. 21, 2015, drama in car No. 12 into a movie, “The 15:17 to Paris."

El Khazzani, a 31-year-old Moroccan, spent several months in Syria and boarded the train in Brussels armed to the hilt, authorities say. He is charged with attempted terrorist murder for the foiled attack. If convicted, he faces a maximum sentence of life in prison.

His lawyer, Sarah Mauger-Poliak, said El Khazzani “regrets having allowed himself to become indoctrinated” by extremist propaganda and wants "to demonstrate his remorse.”

Three others, who weren't on the train, also are being tried as alleged accomplices.

FILE – In this file photo dated Sunday, Dec. 20, 2015, passengers walk through a metal detector at the Grare du Nord train station in Paris, installed in response to a terror attack aboard a train. (AP Photo/Christophe Ena, FILE)

Bilal Chatra, 24, an Algerian member of the Islamic State group, would have been the second man on the train but dropped out of the plot a week earlier. He had left Syria for Europe a week before to set up the exit route.

Mohamed Bakkali allegedly took in the Europe-bound attackers in Budapest, Hungary, which he denies. The two were arrested in Germany in 2016. A third man, Redouane El Amrani Ezzerrifi, allegedly piloted a boat to help in their return to Europe.

The trial serves as a bridge to the massacre of 130 people in Paris three months later, on Nov. 13, 2015, at the Bataclan music hall and restaurants and cafes. The man considered the likely mastermind of those attacks, Abdel Hamid Abaaoud, was the behind-the-scenes force in the train attack, planned in Syria, according to the prosecution.

Abaaoud traveled from Syria to Belgium with El Khazzani to organize attacks in Europe, and was holed up with him and Chatra in a Brussels apartment, according to the prosecution. Abaaoud was killed by French special forces days after the Bataclan attack. But before his death, his macabre organizational skills were at work in a failed plan to attack a church south of Paris in April 2015 that left a young woman dead. Sid Ahmed Ghlam was convicted earlier this month and sentenced to life in prison.

El Khazzani was armed with a Kalashnikov, nine clips with 30 rounds each, an automatic pistol and a cutter, according to investigators.

FILE – In this Aug. 24, 2015 file photo, French President Francois Hollande bids farewell to U.S. Airman Spencer Stone as U.S. National Guardsman Alek Skarlatos of Roseburg, Ore., second from left, and Anthony Sadler, a senior at Sacramento State University in California, right, after Hollande awarded them the French Legion of Honor at the Elysee Palace in Paris. (AP Photo/Michel Euler, File)

Once on the train, he lingered in a restroom between cars and emerged bare-chested with the Kalashnikov. One waiting passenger struggled with the attacker, then a French-American, Mark Magoolian, wrestled the Kalashnikov away — before being shot himself by a pistol as he headed to car No. 12 to warn his wife. Magoolian said in interviews later that the attacker recovered the Kalashnikov.

Spencer Stone, then a 23-year-old U.S. airman, has said he was coming out of a deep sleep when the gunman appeared. He said that Skarlatos, then a 22-year-old U.S. National Guardsman recently back from Afghanistan, “just hit me on the shoulder and said ‘Let’s go.’”

The men, all from California, snapped into action out of what Skarlatos said at a news conference days later was “gut instinct.” Stone and Skarlatos moved in to tackle the gunman and take his gun. A third man, Anthony Sadler, 23, then a student, helped subdue the assailant. Stone said he choked El Khazzani unconscious. A British businessman then joined in the fray.

Stone, whose hand was injured by the cutter, is also credited with saving the French-American teacher whose neck was squirting blood. Stone said he “just stuck two of my fingers in his hole and found what I thought to be the artery, pushed down and the bleeding stopped.”

The train rerouted to Arras, in northern France, where El Khazzani was arrested.

(Material from the Associated Press was used in this report)