The alleged attacker, named as 25-year-old Moroccan national Ayoub El Khazzani, on Friday evening boarded a high-speed train in Brussels bound for Paris armed with a Kalashnikov assault rifle, Luger automatic pistol, nine cartridge clips and a box-cutter.
Witnesses say he opened fire, injuring a man before being wrestled to the floor by three American passengers and tied up, until the train stopped in the northern French city of Arras where he was taken into police custody.
"He is dumbfounded that his act is being linked to terrorism," she told BFM-TV, adding the suspect who is believed to have lived in Belgium describes himself as a homeless man.
"He says that by chance he found a suitcase with a weapon, with a telephone, hidden away," said David, who is no longer representing him as Khazzani has been transferred to Levallois Perret near Paris where he is being questioned by counter terrorism officers.
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"He says that the Kalashnikov didn't work and he was brought under control immediately without a single shot being fired," David added.
Intelligence services in several countries had nevertheless previously flagged him as a radical Islamist, and French investigators are focussing on an extremist attack.
Armed with the weapons, the attacker exited a toilet cubicle on the high-speed train just after it crossed from Belgium into northern France.
A French passenger who happened to be there tried to disarm Khazzani -- described as "small, slim, not very strong" -- but he got away and fired at least one shot, wounding a Franco-American traveller in his 50s.