Social media bosses were summoned by the French government after it emerged the terrorist who beheaded a teacher may have been led to his victim by an online campaign of harassment.
Samuel Paty, 47, was murdered with a butcher’s knife in the street about three hundred metres from the school in Conflans-Sainte-Honorine at around 5pm on Friday.
The married father was targeted for using cartoons of the Prophet Mohammed in a class on freedom of expression A week earlier, one man who said his daughter was in Mr Paty's class recorded a video shared on social media in which he branded the teacher a thug and appealed to others to "join forces and say 'stop, don't touch our children'".
Mr Paty’s name and school address were also put on the internet after he showed the cartoons of a nude Mohammed in class. He suggested any Muslims who might be offended leave the room before showing the images. Islam prohibits images of the prophet, considering that they lead to idolatry.
The killer had approached pupils in the street and asked them to point out his victim, anti-terrorist prosecutor Jean-Francois Ricard said on Saturday.
An 18-year-old Chechen-Russian, named as Abdoulakh Anzorov, posted a photo of his victim’s severed head on Twitter where it was seen by some of his pupils before he was shot dead by police.
One parent Delphine, whose daughter was in Mr Paty's class last year, told The Sunday Telegraph: "My daughter has access to so many concerning websites. She saw the images of the body online, and many of the kids did too. That's what worries me most."
The terrorist, who was not known to intelligence services, was granted a 10-year residency in France as a refugee in March. He was never taught by Mr Paty and lived in Evreux in Normandy.
“From Abdullah, the servant of Allah, to Macron, the leader of the infidels, I executed one of your hell dogs who dared to belittle Muhammad,” he tweeted with a picture of the severed head.
Social media bosses were called to talks at France’s Interior Ministry after what French President Emmanuel Macron called a “blatant Islamist terrorist attack". There will be a national tribute to Mr Paty on Wednesday.
Hundreds of people, many still in shock, gathered around the Bois d'Aulne secondary school on Saturday to pay their tributes to the history and geography teacher.
Surrounded by police, they put flowers on the school's doorstep, they sang the French national anthem and tried to come to terms with the news.
Parents and students pointed to the role social media played in magnifying the controversy over the freedom of expression class Mr. Paty gave two weeks before the murder.
“I can't find the words," said Valerie Lalanne, a Spanish teacher in a high-school in the Yvelines department, where the attack happened. After a sleepless night since learning of Mr Paty's death, she made her way to the school to pay her respects.
"Us teachers, we are the protectors of freedom of expression. We can't back down now," she said, her lips shaking as she tried to speak through tears.
Marjorie Goetz, a 46-year-old neighbour and a civil servant whose son will join the school next year, said,“As a civil servant, now I self-censure and we don't touch on certain issues publicly because we are scared of causing outrage. As a citizen, I'm against censorship. But as a mother, I can't take those risks."
For Muslim residents, the fear of backlash added to the anger over the killing.
"He was my son's teacher. We are here to pay our respects and also show, as Muslims, that we are not like these people," said Stephanie Paris, 33.
“What [Mr Paty] did was great, he tried not to offend anyone, he fulfilled his duty."My own kids asked me 'He's a Muslim, why did he do this?'”
Mr Ricard said, France's anti-terrorist prosecutor said an investigation for murder with a suspected terrorist motive had been opened. The prosecutor said a text claiming responsibility and a photograph of the victim were found on the suspect's phone.
Witnesses told police they heard the killer shouting “Allahu Akbar” [‘God is the greatest’ in Arabic] before he was shot nine times by officers after firing on them with an airgun. No explosives were found on his body after it was checked by a bomb disposal unit.
A total of nine suspects have been arrested. Five suspects were rounded up by police, among them two parents of pupils at the College du Bois d'Aulne, on Friday night and a further four arrested this morning. They include the parents of the killer, his 17-year-old brother and his grandfather.
Our community is horrified like all French people by this incident," said the Strasbourg-based Assembly of Chechens in Europe. It said "that no community can be held responsible for all isolated acts of its nationals ”.
Chechnya is a predominantly Muslim Russian republic in the North Caucasus. Two wars in the 1990s triggered a wave of emigration, with many Chechens heading for western Europe.
Friday's terror attack came as Mr Macron's government works on a bill to address Islamic radicals, who authorities claim are creating a parallel society outside the values of the French Republic. Muslim leaders condemned the killing.
The killing came at a highly sensitive time in France after two people were seriously injured in a knife attack last month outside the former offices of the satirical weekly Charlie Hebdo.
A suspect investigators he had been angered by the newspaper’s decision to republish controversial cartoons of the Prophet Mohammed to coincide with the ongoing trial of 14 alleged accomplices of two Islamists who massacred 12 people at Charlie Hebdo’s offices five years ago.