A second brother of a young French anti-drugs campaigner, Amine Kessaci, has been shot dead in Marseille in a suspected criminal gang killing.

An elder brother was murdered in 2020. Brahim Kessaci was shot and his charred body found in a burned-out car, a common method in gang killings known locally as a barbecue.

Amine, a high school student at the time, then set up an association called Conscience, which aims to help young people in Marseille's poor estates to escape the clutches of powerful drugs gangs.

On Thursday, he learned that a second of his brothers, 20-year-old Mehdi, had also been murdered in the city.

Mehdi was parking his car in central Marseille when a motorcycle drew up and the pillion passenger opened fire with a 9mm pistol.

While Amine's murdered elder brother, Brahim, was known to have become involved with drugs gangs, investigators say that was not true of Mehdi, who had ambitions to become a policeman.

They fear the murder was a warning aimed at Amine.

That hypothesis is absolutely not being ruled out, said Marseille chief prosecutor Nicolas Bessone on French radio.

And if it turns out to be the case, it will mean we have crossed another threshold. It brings back certain terrible periods in our country's history, when you went out and killed people simply because they were from a family with whom you had problems.

Amine Kessaci, who ran unsuccessfully for the Green Party in European and legislative elections last year and recently wrote a book called Marseille Wipe your Tears – Life and Death in a Land of Drugs, has recently received death threats, and he is living under police protection.

It's just so sad for my friend and for his mother, said Christine Juste, a Green Party city councillor in Marseille.

No mother should go through that — losing two children. And I'm so angry that in France's second city, people can be murdered so easily in plain daylight.

Marseille is renowned for its worsening drugs wars, with rival gangs from high-immigration neighbourhoods in the north of the city battling over turf.

Vendettas spawn successions of revenge murders, with killers sometimes as young as 15. So far there have been 14 drugs-related murders this year.

Amine Kessaci's association, Conscience, has branches in several other towns and cities. Its main activities involve providing help and advice to families who have lost sons in drugs violence, and creating links between ex-delinquents and employers.

When he was 17, Amine was selected to meet Emmanuel Macron when the president came to Marseille in 2021 to discuss projects to improve life in the city.

A local newspaper dubbed him in its headline: The kid from the estates who has Macron's ear.

Explaining his decision to run for election the young campaigner wrote in his book: Politics never held out its hand to me, so I decided to grab it by the throat. Brahim – it was you who threw me into politics the day you burned in a car.