Lieutenant-Colonel Arnaud Beltrame, 44, was shot and stabbed after taking the place of a woman whom Radouane Lakdim had been using as a human shield during his attack Friday at a supermarket in the town of Trebes.
The sleepy town of 5,000, located on the picturesque Canal du Midi, is just eight kilometres from the famed medieval walled city of Carcassonne, where a silent march is planned next Saturday, the eve of Easter Day.
The bishop of Carcassonne and Narbonne celebrated the mass in Trebes' Church of Saint-Etienne to honour the four killed and three wounded in the attacks claimed by the Islamic State group.
“We want this to stop,” said Jean-Pierre Bordeaux, who came with his wife Henriette from the nearby village of Capendu to attend the remembrance mass.
“We aren't safe from anything anywhere.”
Parish priest Philippe Guitart warned against blaming Muslims in general for jihadist attacks. “We must… help people to learn to live together,” he said.
Representatives from the Muslim community attended the mass, which had an overflow crowd listening to the service through loudspeakers outside the small church as armed police stood by.
“We have had a long friendship with them,” Bishop Alain Planet said. “They are very aware of this sadness, which affects them as well.”
People laid bouquets of white roses outside the town hall in Trebes, with one message reading “Stop the violence, stop, stop”.
A national tribute will be held at a later date for Beltrame, who President Emmanuel Macron said had “died a hero” and deserved “the respect and admiration of the whole nation”.
Beltrame's brother Cedric said the policeman would have known all too well the risk he was taking. “He certainly knew he didn't stand a chance,” he said.
“He gave his life for another.”
Following the worst jihadist attack of his presidency, Macron has called a meeting later this week of the security services who monitor individuals suspected of radicalisation.
Lakdim, 25, a petty criminal, was on a watchlist, but authorities had concluded the Moroccan-born French national did not pose a threat.
Investigators found notes referring to Islamic State (Isis) at Lakdim's home in Carcassonne, a legal source said, including a hand-written letter in which he claimed allegiance to the jihadist group.
Lakdim, who was armed with a gun, knife and homemade explosive devices according to a security source, was shot dead as police moved in to end his siege of the Super U supermarket where he had holed up after a shooting spree in Carcassonne.
Earlier Friday the gunman had hijacked a car in Carcassonne and shot the two people inside, killing the passenger and leaving the Portuguese driver in a critical condition.
He also shot and wounded a police officer out jogging.
Lakdim had already shot dead the supermarket's butcher and a customer when Beltrame offered to take the place of a woman he had taken hostage.
Lakdim shot and stabbed the policeman before he was himself killed by anti-terror officers.
Beltrame died of his wounds early Saturday, becoming the fourth victim in the shooting spree.
The shootings come as France, part of the US-led coalition fighting Isis, remains on high alert following a string of deadly attacks that have killed more than 240 people since 2015.
Lakdim fit a familiar profile as a petty criminal who had turned to extremism.
A small-time drug-dealer, his rap sheet included convictions for carrying a banned weapon and for drug use. He spent a month in jail in 2016.
His girlfriend and a 17-year-old friend were in custody.
According to a source close to the investigation, Lakdim had hinted at travelling to Syria in 2014, but did not go.
During the attacks, he demanded the release of certain prisoners — notably, according to a security source, Salah Abdeslam, the prime suspect in the November 2015 Paris terror attacks.
Isis claimed Friday's attack was in response to its call to target Western enemies, as is customary when the assailant has pledged allegiance to the jihadists.