"(I saw) somebody who was very sick, somebody very weakened physically, as if he suffered from malnutrition, very, very thin and very haggard," David told BFMTV.
"He is dumbfounded by the terrorist motives attributed to his action," she added.
David said the man was barefoot and wore only a hospital shirt and boxer shorts for the police interrogation in Arras, northern France, where the train stopped after the incident.
The Moroccan told David he had found the Kalashnikov he had taken onto the train in a park near the Gare du Midi rail station in Brussels where he was in the habit of sleeping.
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"A few days later he decided to get on a train that some other homeless people told him would be full of wealthy people travelling from Amsterdam to Paris and he hoped to feed himself by armed robbery," David said.
The lawyer said the Moroccan had untreated wounds on his face when he spoke to her through an interpreter. He also told David he did not think he had fired any shots before his gun jammed.
French Interior Minister Bernard Cazeneuve said on Saturday there had been "several shots" before the Moroccan was subdued by the passengers, who included three Americans.
Of the two passengers injured in Friday's incident, only one remained in hospital on Sunday, according to an update from the authorities -- a Franco-American who was hit by a bullet and was in a serious but stable condition.
Cazeneuve said the man in custody, whom he did not name, had been "identified by the Spanish authorities to French intelligence services in February 2014 because of his connections to the radical Islamist movement".
Arrests for drug offences
Khazzani is believed to have lived in Spain for his early adult life and was arrested at least once for drug trafficking, according to Reuters sources. Some Spanish newspapers said he may have been radicalized while in prison.
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Spanish security sources say Khazzani lived in Madrid between 2007 and 2010 before moving to the southern Spanish port of Algeciras. A community leader in the city told Reuters he had lived there with his family in El Saladillo, a neighborhood plagued by high unemployment and drug-related crime.
According to the Spanish security sources, he traveled to France in 2014 and went to Syria. French security sources said he went to Berlin airport for a flight to Istanbul on May 10 this year. Turkey is a preferred flight destination for would-be jihadists heading for Syria.
At the mosque in El Saladillo, Kamal Cheddad, President of the Muslim Community for the south of the city, said he knew the young Moroccan, although the family did not attend the local mosque which Cheddad presides over.
"He was an ordinary young man, he played football, went fishing, he worked to make a living," Cheddad said.
Meanwhile, French President Francois Hollande on Monday will award France's highest honour, the Legion d'honneur, to the three U.S. citizens and a Briton who helped disarm Khazzani.
The award will be made when Hollande meets the men in the morning local time, a member of the president's entourage said after it was revealed that one of the Americans, Spencer Stone, likely also had saved the life of a fellow passenger.
Stone, a 23-year-old airman travelling with two friends on the train from Amsterdam to Paris on Friday, told reporters on Sunday of how he plugged the blood-spurting wound of another passenger with his fingers after himself being injured by the attacker.
Stone was traveling with student Anthony Sadler, also 23, and National Guardsman Alek Skarlatos, 22. They will be honored alongside Chris Norman, a 62-year-old British consultant who lives in France.
Stone said another man, who is French and whose name has not been disclosed, "deserves a lot of the credit" because he was the first one to try to stop Khazzani. Stone also thanked the doctors who reattached his thumb, which was almost severed by the gunman, who was armed with a box cutter, a pistol and the Kalashnikov AK-47assault rifle.
The Americans, who grew up together near Sacramento, California, were touring Europe, partly to celebrate Skarlatos' return from a recent tour of duty in Afghanistan.
At the Sunday press conference, Skarlatos disputed a statement the gunman made through a lawyer, that he just wanted to rob the train because he was hungry.
"It doesn't take eight magazines to rob a train," Skarlatos said. "The guy had a lot of ammo. His intentions seemed pretty clear."