The French government raised its terrorist threat alert to the highest level on Friday after a knife-wielding man killed a teacher and injured three other people at a school in northern France in what officials described as an Islamist terror attack, deeply disturbing the country.
The attack put President Emmanuel Macron’s government under intense pressure as officials acknowledged that the main suspect in the attack and several of his family members had been identified by intelligence services as radicalized or had been convicted on terrorism charges.
The suspect was even taken in for questioning the day before the assault, officials said, but was let go after it was determined that he did not pose an immediate threat.
The stabbing took place at the Gambetta-Carnot public school in Arras, a town of about 42,000, roughly 25 miles southwest of Lille, near the Belgian border.
The suspect was identified by officials only as Mohammed M., a Russian immigrant born in 2003, who had previously attended the school. He was quickly arrested at the scene, which includes a middle and a high school, and antiterrorism prosecutors opened an investigation.
Attacks on schools are rare in France, but this one struck a particularly raw nerve. The country is still haunted by the murder of Samuel Paty, a 47-year-old history teacher who showed caricatures of the Prophet Muhammad in class to illustrate free speech and was beheaded by an Islamist extremist because of that on Oct. 16, 2020.
“Almost three years to the day after Samuel Paty’s murder, terrorism has struck again in a school,” President Emmanuel Macron, looking somber, told reporters in Arras after rushing to the scene.
Government officials and school colleagues identified the victim as Dominique Bernard, a French literature teacher, and those injured as a physical education teacher and two other school employees.
“We stand together and stand tall,” Mr. Macron said, against the “barbarity of Islamist terrorism.”
The victim was killed in a “brutal and cowardly way,” said Mr. Macron, who praised the surviving teacher for trying to stop the assailant.
Lawmakers in the lower house of Parliament rapidly suspended their work in solidarity with the victims and then observed a moment of silence.
The government announced, after an emergency cabinet meeting later on Friday, that it was putting the country on the highest of its three threat levels.
Gérald Darmanin, the interior minister, said in an interview on TF1 television that the move was precautionary and authorities had not detected any specific threats.
But Mr. Darmanin added, without elaborating, that based on information gathered by French authorities, there was “probably” a link between the attack and the ongoing conflict between Israel and Hamas — part of an “extremely negative atmosphere,” he said.
The attack quickly raised questions about security in schools — a teacher was killed by a student at a high school in February, although terrorism was ruled out in that case. Gabriel Attal, the education minister, said security would be reinforced at schools around the country.
Jean-François Ricard, France’s top antiterrorism prosecutor, said at a news conference in Arras on Friday that the assailant arrived in front of the school around 11 a.m. There, he stabbed two teachers: the one who later died, and another who tried to intervene.
The assailant then entered the school — which was in between periods, meaning the doors were open to let students in or out — and shortly afterward arrived in a courtyard, where several school employees tried to stop him. Two of them, a technical employee and a cleaning worker, were wounded, Mr. Ricard said.
Several witnesses heard the assailant shout “God is great” in Arabic during the attack, he added.
“Many investigations are ongoing and must continue to determine exactly how the events unfolded, how the assailant prepared his crime and what potential help he was given,” Mr. Ricard said, adding that several people were currently in custody for questioning.
Martin-Roch Doussau, a philosophy teacher who has taught at the school for five years, described the school as usually calm and with a positive atmosphere.
In a phone interview, Mr. Doussau said that he confronted the attacker in the schoolyard. The attacker had two knives and turned to him, asking if he was a history professor, he said. Mr. Doussau barricaded himself behind a door with another teacher until police officers arrived and used stun gun devices to apprehend the assailant.
Mr. Doussau said that the man did not appear to be targeting specific people, though he seemed intent on finding a history teacher. Mr. Paty’s killing immediately came to mind, Mr. Doussau said.
A teacher’s job in France, he said, is to embody France’s universalist values and to promote fraternity among students.
“Our job is to avoid things like this,” he said.
France was struck by large-scale Islamist terror attacks in 2015 and 2016, followed by a string of smaller but still deadly shootings and stabbings in subsequent years, often carried out by lone assailants.
The country remains on high alert, and the government says that the police and intelligence services have thwarted over 40 terrorist plots since 2017.
“We are in a moment where police protection is extremely strong and extremely firm,” Mr. Darmanin said.
But the profile of the suspect in the attack in Arras quickly sparked a firestorm of criticism from Mr. Macron’s political opponents, who said the authorities should have seen it coming.
Mohammed M. had been flagged in France’s S Files, a database of people believed to be threats, but who are not necessarily being monitored around the clock.
“This new attack symbolizes the powerlessness of our State in the face of the Islamist scourge,” Olivier Marleix, a top lawmaker for the right-wing Republican party, said in a statement.
Jordan Bardella, the head of the far-right National Rally party, said the government was responsible for a “moral, political and security failure.”
“It is no longer acceptable for the government to inflict upon the French an impossible coexistence with human bombs,” Mr. Bardella said in a video statement.
Mr. Darmanin, the interior minister, said that intelligence services had recently been tipped off that Mohammed M. had been in touch with other radicalized people, including his brother.
That prompted intelligence services to tap his phone and place him under surveillance, Mr. Darmanin said. But they did not detect any immediate plans to stage an attack.
The police briefly took Mohammed M. into custody on Thursday to verify that he did not have a weapon and to check his phone, but the officers did not find any signs of an immediate threat, Mr. Darmanin said.
Still, Mr. Darmanin acknowledged that Mohammed M.’s family had repeatedly come across the radar of French security services.
Mohammed M.’s father, who had also been flagged for radicalism, had been deported in 2018, he said. Under French law, although there are exceptions, Mohammed M. could not be deported because he had arrived in France before the age of 13, Mr. Darmanin said, adding that he hoped to lift that obstacle with an upcoming immigration bill.
Mr. Ricard, the prosecutor, said that Mohammed M.’s older brother was in prison after being convicted in April for taking part in a terrorist criminal conspiracy and again in June for glorifying terrorism, and that the two brothers were close. He did not provide more details about those cases.
“We knew that there was fertile ground, and radicalization difficulties,” Camille Chaize, the interior ministry spokeswoman, told BFMTV on Friday. But without intelligence pointing to a specific plot, she added, “how do you detect the moment when someone acts?”
Catherine Porter contributed reporting.