PARIS (Reuters) - A man who died when he rammed his car into a police van in Paris this week told people he joined a gun sports club to prepare as a jihadi fighter, France’s top public prosecutor said on Thursday.

Police secure the area near a burned car at the scene of an incident in which it rammed a gendarmerie van on the Champs-Elysees Avenue in Paris, France, June 19, 2017. REUTERS/Charles Platiau

Prosecutor Francois Molins did not explain how the assailant he named as Adam D. managed for years to obtain gun permits and renew them, even after his name was put on a secret service list of potentially radicalized individuals.

It is a question that remains unanswered as investigators probe the latest of a string of attacks by Islamist assailants who have killed more than 230 people in France since early 2015.

Molins said the attacker on the Champs Elysees on Monday appeared to have died of a cardiac arrest and inhalation of toxic fumes. TV footage showed clouds of orange smoke spewing out of his vehicle after he drove it into the police van.

In the car police found a copy of a letter the attacker had sent the same day to several people, in which he swore allegiance to the leader of the Islamic State militant group and said he had joined a gun club years ago, not for the sport but to prepare for jihadi combat.

He had a Sig Sauer pistol strapped to his body and the car was laden with two gas tanks, rifles, knives and thousands of rounds of ammunition.

“The scale of the arsenal found in the vehicle shows the size of the planned terrorist attack and the dramatic human cost it could have inflicted,” Molins said.

Married to a Tunisian woman and father of two children, Molins said the assailant had traveled frequently to Turkey, one of the main transit points foreign jihadists use to get to Islamic State bases across the border in Syria.

He was stopped several times, on occasion with his family, and explained each time that he was a gem dealer. Once he was stopped in possession of a bar of gold and said it was part of his business, Molins said.

A raid this week on his home unearthed a vast stash of other weapons and materials that could be used to make a bomb.

On April 20 an Islamist shot dead a policeman in a police vehicle parked on the Champs Elysees. The attacker was then killed in a shootout with police.