When a Tunisian-born man drove a 19-ton rented truck into a crowd of revelers celebrating France’s national holiday in the Mediterranean town of Nice last week, killing 84 people and injuring hundreds more, it was a deadly new example of an old terrorist tactic of turning vehicles into weapons, according to Stanford experts.

French authorities identified the man behind the wheel as Mohamed Lahouaiej Bouhlel, a 31-year-old immigrant from Tunisia who had lived in France since around 2005 and had been working as a delivery driver. Police shot him dead on the scene.

Martha Crenshaw, a senior fellow at Stanford’s Center for International Security and Cooperation (CISAC), said the fact that Bouhlel already had a commercial driver’s license gave him easy access to his weapon of choice.

“It was just unfortunate that he was somebody who already drove big trucks,” said Crenshaw.

“He did not have to go do something special, like train for a pilot’s license in the way that the 911 hijackers did, in order to acquire the means to kill people.”

Vehicles as tools of terror

Crenshaw said there had been around 30 incidents worldwide since 1994 where terrorists used vehicles as their primary weapon in attacks on civilians (not including car and truck bombs where explosives were used). Crenshaw noted that not all those vehicle attacks caused casualties.

If you include assaults on police and military targets, there have been more than 155 attacks where a vehicle has been used as a weapon in the way the truck was used in Nice, with over 75 of those attacks occurring in just the last three years, according to data from the National Consortium for the Study of Terrorism and Responses to Terrorism (START).

However, the exceptionally high number of casualties puts the attack in Nice in a league of its own. Most of the vehicle attacks on police and military only result in one or two casualties at a checkpoint or other hard target.

Stanford terrorism expert and former U.S. Special Forces Colonel Joe Felter said he was concerned that the attack in Nice “lowered the threshold” for aspiring terrorists who would be motivated to carry out copycat attacks.

“This was a disturbingly effective attack,” said Felter, a senior research scholar at CISAC.

“The message for would-be terrorists is that you don’t have to become a bomb maker to successfully execute a mass casualty attack. With a driver’s license and a credit card you can weaponize a rental truck.”

A challenge for law enforcement

Former CISAC fellow Terrence Peterson said it would be particularly difficult for law enforcement agencies to prevent terrorists from gaining access to vehicles.

“The types of people who would show up on other lists…like the no-fly list, are not going to show up when they rent a car,” said Peterson.

“A car is such a mundane object. How do you control using an everyday object for a terrorist attack? It’s nearly impossible.”

Al Qaeda had previously advocated using pickup trucks to target civilians, in the “Open Source Jihad” section of its propaganda magazine “Inspire.”

“The idea is to use a pickup truck as a mowing machine, not to mow grass but mow down the enemies of Allah,” according to a translation on the Web site MEMRI Cyber and Jihad Lab, which tracks jihadist postings online.

The article also advised would-be terrorists to, “pick your location and timing carefully. Go for the most crowded locations. Narrower spots are also better because it gives less chance for the people to run away…Therefore, it is important to study your path of operation before hand.”

French prosecutors said that Bouhlel carried out surveillance of the Promenade des Anglais prior to his attack there, and that he conducted online research into the mass shootings in Orlando and Dallas.

Murky motivations

It is still unclear what motivated Bouhlel. He had a history of domestic violence, psychological problems and money troubles, according to media reports. Acquaintances said the divorced father of three was not an outwardly religious Muslim. He reportedly drank alcohol, used drugs, ate pork and had sexual encounters with other men, all of which are forbidden under strict interpretations of Islam.

However, French authorities have suggested that he may have undergone a rapid conversion to radical Islam. And a Web site affiliated with the terror group ISIS has claimed Bouhlel as “a soldier of the Islamic State.”

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The apocalyptic ideology of jihadist groups like the Islamic State (also known as “Daesh”) could be particularly appealing to “petty criminals, psychologically deranged or otherwise lost souls” such as Bouhlel, said David Laitin, James T. Watkins IV and Elise V. Watkins professor of Political Science.

“Spurred by Salafist propaganda, these recruits can work privately, away from any institutional connection with Daesh, to cause horror,” Laitin said.

“And many police forces are out of touch with vulnerable populations and are slow to identify potential recruits.”

"Confrontation is unavoidable"

Regardless of Bouhlel’s motivation, his attack would likely bolster the anti-immigrant agenda of France’s far-right political parties such as the National Front, which advocate policies such as closing the borders, exiting the European Union and deporting bi-nationals with links to Islamist groups, said Cécile Alduy, associate professor of French and an affiliated faculty member with the Europe Center at the Freeman Spogli Institute for International Studies.

“The attacks will only strengthen the feeling that the political elites in power failed, and that the National Front “told us so” and are the only ones left to trust,” Alduy said.

Patrick Calvar, the head of France’s counter-terrorism intelligence agency DGSI, warned earlier this year that the recent series of terror attacks on French soil could trigger “inter-ethnic clashes” between far-right vigilante groups and Muslims living in France.

“One or two more terrorist attacks” and “the confrontation [between the two sides] is unavoidable,” said Calvar.

Alduy said she feared the shift in French public opinion could make Calvar’s prediction more likely.

“An opinion poll…in March 2015 put “sadness” as the primary feeling that respondents identified with following the Charlie Hebdo attacks,” Alduy said.

“After the November attacks, it was “anger”, with “hatred” following closely for over 60% of them. Now what will it be?”