The man was stopped yesterday when a soldier fired and wounded him. France is on high alert after the coordinated attacks by Islamic extremists in Paris on Nov 13.
Prosecutor Alex Perrin said today "so far it seems to be the act of an individual."
Perrin said the 29-year-old French citizen of Tunisian descent is a practicing Muslim not reported as radicalized. He was not known to the police and justice services and has no psychiatric history. His motives remain unclear.
He notably said "Allahu Akbar," or "God is great," which "shows a link with a certain religiosity," Perrin detailed.
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No weapons or explosive devices have been found inside his car.
The man, who is still hospitalized, could be charged in coming days with "attempted murders against persons holding state authority."
The attacker twice rammed his car into the soldiers guarding the main mosque in Valence, the prosecutor said, charging once then putting his car into reverse to try to ram the soldiers again.
One soldier was slightly injured in the leg, and a passerby was hit in the leg by a stray bullet.
France has been in a state of emergency since the Nov 13 Paris attacks, claimed by the Islamic State group, that killed 130 people and injured hundreds more. The soldiers by the mosque are part of the reinforced security guarding places of worship and other sensitive sites around France.