Police have named the suspect as Abdoulakh A, an 18-year-old man born in Moscow of Chechen origin. No details have been given about the latest person detained by the French authorities.
Four close relatives of the suspect were arrested shortly after the killing. Six more were detained on Saturday, including the father of a pupil at the school and a preacher described by French media as a radical Islamist.
President Emmanuel Macron said the attack bore all the hallmarks of an “Islamist terrorist attack” and the teacher had been murdered because he “taught freedom of expression”.
The murder has appalled France. Demonstrations are planned across the country on Sunday denouncing the attack, and there will be a national tribute paid to Mr Paty on Wednesday.
“A civilisation does not kill an innocent person, barbarism does,” Tareq Oubrou, imam of a mosque in Bordeaux, told France Inter on Saturday.
And Laurent Nuñez, the head of France’s anti-terrorism task force, told France Info radio: “A threshold has been crossed”, citing the attack on “the freedom to teach” and “the barbarity of the act”.
What happened on Friday?
Anti-terrorism prosecutor Jean-François Ricard told reporters that the suspect lived in the Normandy town of Évreux, about 100km (60 miles) from the murder scene.
The man went to the school on Friday afternoon and asked students to point out the teacher. He had no apparent connection with the teacher or the school.
He then followed Mr Paty as he walked home from work. The suspect used a knife to attack the teacher in the head, and then beheaded him.
Witnesses are said to have heard the attacker shout “Allahu Akbar”, or “God is Greatest”.
As police approached him, he fired at them with an airgun. Officers returned fire, hitting him nine times. A 30cm-long (12in) blade was found close by.
Authorities said the man had been before courts but only on minor misdemeanour charges.
What’s the latest in the investigation?
Mr Ricard said Mr Paty had been the target of threats since he showed the cartoons of the Prophet Muhammad during a class about freedom of speech, in relation to the Charlie Hebdo case.
The French satirical magazine was the subject of a deadly attack in 2015 after publishing the cartoons. A trial over that attack is currently under way.
As he had done in similar lessons in recent years, Mr Paty, a history and geography teacher, advised Muslim students to look away if they thought they might be offended.
A parent of one of the pupils reacted angrily, and went to the school to complain. He and another man who accompanied him – Abdelhakim Sefrioui, a preacher and activist – made videos calling Mr Paty a “voyou” (thug) and demanding his suspension.
Mr Sefrioui has reportedly been known to French intelligence services for years. Both he and the father are now in custody.
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