Suspect was killed by police after onslaught left at least 84 people dead
Photographs from the scene show the vehicle's windscreen riddled with gunshots.
The attacker fired a pistol several times into the crowd after the truck was brought to a halt, according to the regional president.
"At the moment that he was shot dead by police, he had fired several times," Christian Estrosi said.
He later said Bouhlel had been picked up on CCTV cameras getting into the truck "in the hills of Nice".
Mr Estrosi added that authorities were looking for any accomplices.
"Attacks aren't prepared alone. Attacks are prepared with accomplices," he said. "There is a chain of complicity. I expect it to be unveiled, discovered and kept up to date."
Earlier, authorities said they had found "grenades and larger weapons" in the truck, which had picked up speed and travelled along the famous Promenade des Anglais for more than a mile.
However, a source close to the investigation told AFP that rifles in the vehicle were "fake" and the one grenade was "inactive".
Footage shows the lorry barrelling down the road, as several people chase after it on foot. Gunshots can be heard.
Three days of national mourning have been declared in France, and it is reported the Eiffel Tower will be illuminated in the colours of the French flag over the coming days:
Mayor of Paris says the Eiffel Tower will be illuminated in red, white and blue during the three-day period of national mourning #NiceFrance— Sky News Newsdesk (@SkyNewsBreak) July 15, 2016