Ayoub El-Khazzani, 25, was carrying 270 bullets for his assault rifle and a bottle of petrol, prosecutor Francois Molins told reporters on Tuesday.
The Moroccan’s phone showed that he had watched a jihadist video shortly before launching the attack, Mr Molins added.
Prosecutors have now filed formal charges against him.
Mr Khazzani is accused of carrying out a “targeted and premeditated” jihadist attack.
He is also accused of firearms offences and “participation in a terrorist association with a view to organising one or several damaging crimes,” according to prosecutors’ documents quoted by the AFP news agency.