Radouane Lakdim – who killed four people and injured 16 others in a shooting-spree and supermarket hostage-taking in south west France – had been known to police and intelligence services for drug offences and illegal firearms. In recent years he drew deeper scrutiny by investigators worried he was at risk of Islamist radicalisation

Born in Morocco, the 25-year-old had French nationality and lived in an apartment on the Ozanam housing estate in Carcassonne, a poor neighbourhood in the grand and picturesque walled town that is one of the historic tourist hotspots of the south.

Lakdim was known to police for small-time drug dealing and drug use. He had been found guilty of carrying a prohibited weapon in 2011 and later for drug use and refusing a court order in 2015. He served a short prison sentence in Carcassonne in 2016.

When Lakdim burst into the busy supermarket on Friday, shouting that he was a soldier from Islamic State, one witness described him laughing as he opened fire, killing a worker from the butcher counter and a customer. Lakdim declared he was ready to die for Syria and demanded freedom for his “brothers”. The French authorities are studying Islamic State’s claim that it was behind the attack.

The French government have firmly described Lakdim as acting alone. It is not clear if he ever had any links to the significant jihadist networks in the south of France that have been targeted by police in recent years, in nearby Toulouse and across the south-east.

But in the summer of 2014 Lakdim had been put on a watchlist of people considered possible extremists. “He was added to the list because of his radicalisation and his links with the Salafist movement” of ultra-conservative Islamism, said Francois Molins, France’s top anti-terror prosecutor.

Lakdim had reportedly been active on social media networks. But in 2016 and 2017 he was the subject of an investigation by intelligence services, “which did not bring to light any sign that would indicate he would carry out a terrorist act”, Molins said.

The French interior minister Gérard Collomb said Lakdim had suddenly moved to carry out the attacks and there had been no sign he would do so. He said security services had not seen signs of radicalisation.

There are around 20,000 people on the same kind of watchlist. Of those, around 11,000 are given special attention. Le Monde reported that Lakdim had initially been in the more serious group, marked out for monitoring by central intelligence services.

Lakdim’s method of targeting police or military conforms to a pattern of attacks on police officers and soldiers, from the shooting spree of the Toulouse terrorist Mohamed Merah in 2012 who first targeted soldiers before attacking a Jewish school, to an attack last year when a police officer was killed on the Champs Elysées. The police barracks where Lakdim shot at four officers from a riot police squad out jogging — very seriously injuring one of them — was not far from his housing estate.

Lakdim’s estate has seen an increase in recent years of the kind of drug-dealing and vandalism that have blighted many poor districts across France.

“We’ve been alerting the authorities for a while now, there’s dealing, there are guns going around, we hear gunshots,” one retired woman told AFP.

Others said it was no worse than other housing estates and there had been no signs of radicalisation with Lakdim or other youths.

“He wore a beard but he was just a regular kid,” one neighbour said.

“He came out twice a day to walk his dog; we were really surprised to learn it was him.”

Lakdim’s trajectory appears to have followed a familiar pattern in France over recent years of young men progressing from petty crimes into terrorism, often after spells in French prisons, and despite surveillance by the authorities.

Since the January 2015 massacre at the Charlie Hebdo newspaper in Paris by two men claiming allegiance to al-Qaida, more than 240 people have been killed in jihadist attacks.

In June 2016 in Carcassonne itself, after months of surveillance police arrested a 22-year-old man on suspicion of planning to target American and Russian tourists.

The French president, Emmanuel Macron, insisted on Friday that the current terrorist threat in France had changed from two or three years ago when attacks were ordered and coordinated from Syria or Iraq, such as the Paris attacks in November 2015 that killed 130 people. Now, he said, there was an internal threat from lone radicalised individuals at home in France.

The prosecutor Molins said: “The acts carried out today sadly remind us once more, tragically, that the terrorist threat level on our territory has not lessened … Now mainly internal, it is firstly the result of radicalised individuals living in our country.”

With Agence France-Presse