Olivier Christen, head of the National Anti-Terrorism Prosecutor's Office said the suspect told investigators he had chosen the location for his attack because he believed Trappes was a stronghold of Islamists.
The 39-year-old, known as Kevin T, is due to appear before a judge on Thursday for formal charges to be considered.
Christen said his department has asked for Kevin T to be held in pre-trial detention.
A 26-year-old man of Congolese origin, Pengo Bossio Wangi, was killed during the attack. Seven people were injured, four of them seriously, including an 11-year-old girl.
"Three of them are still in hospital and one remains in a life-threatening condition,” said Christen.
He said that Kevin T denied any terrorist intent and considered his actions legitimate.
"He denied having wanted to kill children and said he may have misjudged the age of the 11-year-old victim based on the child's size. He has expressed no regret."
Suspect in deadly Paris suburb shooting moved to psychiatric unit
Possible charges
The charges under consideration include “murder and attempted murder in connection with a terrorist enterprise, with the aggravating circumstance that the offences were committed because of the victims' real or perceived membership of a purported race, ethnic group, nation or particular religion”.
A search of the suspect's home following the attack uncovered a booby-trap device, as well as weapons or weapon components.
Christen said a magazine, two knuckle-dusters, a steel bayonet and a silencer were found, along with books including a Quran, a Bible and a copy of Adolf Hitler's Mein Kampf.
Stickers were found with slogans including “Long live France, RN, proud to be French", “100% French/long live France” and “Support for law enforcement”.
National tribute
On Wednesday, the government announced that Prime Minister Sébastien Lecornu will preside over a national tribute to the victims of the attack.
“Given that some of the victims are still fighting for their lives, the arrangements for this tribute have yet to be finalised," said government spokeswoman Maud Bregeon.
Cyrielle Chatelain, leader of the Green group in France's National Assembly, had called for a national tribute to the victims on Tuesday during parliamentary questions.
Trappes mayor Ali Rabeh hailed President Emmanuel Macron for visiting the town following the shootings.
“I want to sincerely thank the president for giving this racist crime all the gravity and solemnity it demands," he posted on social media. “May the strength of this national tribute lead our country back towards harmony."
(with newswires)



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