NICE • As French investigators try to piece together what drove Mohamed Lahouaiej Bouhlel to such extreme violence, many people in Nice and around the world are asking how, in a country under a state of emergency since November, a lone driver could so easily flout basic traffic rules and then race unimpeded through throngs of people gathered to watch a Bastille Day fireworks display.
As in previous years, security forces, worried about a possible terrorist attack on France's national day, set up barriers to block traffic on the Promenade des Anglais, a boulevard that stretches eastwards from the city's airport to its old port.
But the barriers, crowd-control devices made of hollow metal tubes, started far to the east of where Bouhlel entered the boulevard. The number of police officers on duty that night was more than usual, but nearly all were concentrated in the sealed-off area by the old port, where most people traditionally gather to watch the fireworks.
This left Bouhlel nearly 2km of open road on which to crush revellers outside the heavily guarded spectator zone - and build up speed before he reached the first police barriers. Such was the 19-tonne truck's speed that when it first encountered any obstruction by police, "it would have required a wall of concrete" to stop it, regional government official Anthony Borre told local television.
"Why was he allowed to drive so far without anyone bothering him?" asked Mr Pierre Roux, who watched the truck plough through the crowd from his balcony. "This is a terrible screw-up," he said.
How big a screw-up is still being deciphered. It is not clear, for instance, whether police tried to shoot out the tyres before being able to shoot the driver, or whether smaller cities around France prepared for the possibility of a large-scale terrorist attack with the same vigilance as Paris, the scene of two major attacks last year.
There, in stages starting early on France's July 14 national day, police snapped in place a security perimeter extending many blocks from the fireworks display at the Eiffel Tower. They closed even major thoroughfares to vehicles, including scooters, and set up checkpoints.
The question of whether more could have been done to prevent 84 people from being killed has been taken up by local leaders on the French Riviera, most of whom represent right-wing forces opposed to the Socialist government in Paris.
France's Socialist government has responded angrily to such criticism, pointing out that nobody expected a rampage by truck and that the attacker had never popped up on the radar of intelligence services.
NEW YORK TIMES