Jean-Francois Ricard told a press conference late Thursday that the man arrived in Italy by reaching the Mediterranean island of Lampedusa on Sept. 20, and traveled to Paris on Oct. 9.
The travel information came from a document on the man from the Italian Red Cross, Ricard said. The attacker was seriously wounded by police and is being treated in a hospital.
The attack in Mediterranean city of Nice was the third in two months in France that authorities have attributed to Muslim extremists, including the beheading of a teacher.
It comes during a growing furor over caricatures of the Prophet Muhammad that were republished in recent months by the satirical newspaper Charlie Hebdo _ renewing vociferous debate in France and the Muslim world over the depictions that Muslims consider offensive but are protected by French free speech laws.
Ricard detailed the gruesome scene encountered inside the Nice basilica where a man and woman were killed by the attacker. The third victim, a 44-year-old woman who managed to flee, died at a nearby restaurant.
A 60-year-old woman whose body was found at the entry of the church, suffered “a very deep throat slitting, like a decapitation,” Ricard said. The 55-year-old man also died after deep cuts to his throat, the prosecutor added.
An investigation was opened for murder and attempted murder in connection with a terrorist enterprise, a common term for such crimes. The prosecutor said the attacker, who was born in 1999, was not the radar of intelligence agencies as a potential threat.