PARIS: Police in France arrested a second person for Friday's attacks by a gunman, which led to the death of four people.
A report by state-run France Info radio said the young man, born in 2000 and a friend of the gunman, Redouane Lakdim, was placed in custody.
Lakdim began his rampage by hijacking a car in the southern French town of Carcassone. He shot one passenger dead and injured the driver.
In Carcassone, he also fired at jogging police officers, injuring one, before driving to nearby Trebes. He stormed a supermarket there, telling the 50-odd people inside that he was "a soldier of the Islamic State" and was seeking "to liberate brothers".
Later, 25-year-old attacker Lakdim was shot dead by the police. He was initially believed to have acted alone.
The death toll climbed to four after a police officer who voluntarily took the place of a hostage during the supermarket siege died on Saturday, the BBC reported.
Lt. Col. Arnaud Beltrame, 44, "fell as a hero" and showed "exceptional courage", French President Emmanuel Macron said.
Col. Beltrame's death was announced on Twitter by French Interior Minister Gérard Collomb. In a radio interview, Col. Beltrame's brother, Cedric, said Arnaud's actions were "beyond the call of duty".
"He gave his life for strangers. He must have known that he didn't really have a chance. If that doesn't make him a hero, I don't know what would," he said.
Earlier, Macron had revealed that Col. Beltrame suffered serious injuries and was fighting for his life in hospital. Sixteen people were injured, two seriously, in what Macron called an act of "Islamist terrorism".
Lakdim was said to have demanded the release of Salah Abdeslam, a key surviving suspect in the November 2015 attacks in Paris, which killed 130 people.
Initially, an 18-year-old woman was taken into custody for criminal association.
Lakdim was known to police for robbery and drug trafficking. He had been on the terror watch list since 2014 for links to the Salafist movements but had not showed any signs suggesting he would plan a terror attack, Paris Prosecutor Francois Molins said.
The Islamic State group has claimed responsibility for the attack. French security services were checking the claim's authenticity.