Eleven people are in custody after police in a Paris suburb shot to death a man seen carrying a knife that authorities believe may have been used to kill another man found nearby.
The shooting of the suspect, 18, occurred around 4 p.m. local time on Friday in the town of Eragny in the Val d'Oise. France's Anti-Terror Prosecutor's Office confirmed to ABC News that it has opened an investigation into whether the killing is linked to terrorism.
The victim was beheaded, authorities said. He was a male teacher at a local middle school who had received threats after mentioning the controversial Charlie Hebdo cartoons depicting the Prophet Mohammed during a lesson, according to police. The lesson prompted a complaint from one of the parents.
Speaking Friday night from the middle school, French President Emmanuel Macron said the teacher was the victim of a "blatant Islamist terrorist attack."
"One of our fellow citizens ... was murdered today for teaching, for teaching students freedom of speech, freedom to believe and not to believe," he said. "It is no coincidence that this evening it is a teacher that this terrorist killed because he wanted to bring down the Republic in its values."
The victim was identified by authorities as Samuel Paty, 47, a professor of history and geography at the middle school, College du Bois d'Aulne.
The suspect had asked students in front of the school to help him identify the victim, according to authorities. Paty was attacked in the immediate vicinity of the school while on his way home and also had multiple wounds on his head, in the abdomen and upper limbs, authorities said. A bloodied knife was discovered a few meters from the scene of the crime, police said.
The national police responded shortly after 4 p.m. local time on Friday following the discovery of a body, authorities said. The suspect was seen running toward the police officers, firing what looked like a pistol five times, which turned out to be a toy air gun, authorities said. Three officers fired back, causing the suspect to fall, police said. While trying to get up, the suspect attempted to stab the officers who neutralized him, authorities said. The suspect was hit by nine bullets, anti-terrorism state prosecutor Jean-François Ricard said during a press briefing Saturday.
The suspect was identified by authorities as a Moscow-born Chechen refugee who had a French residence permit. He was unknown to intelligence services, authorities said.
The teen claimed responsibility for the attack on Twitter in a post that referred to the victim by name and included a macabre photo of him, Ricard said. "I executed one of your hellhounds who dared to belittle Muhammad," part of the post said, according to authorities. The account has since been suspended.
Eleven people are in police custody, including four members of the suspect's family, authorities said. The student's father who complained about the teacher's lesson and a second man who came with him to the middle school are in custody. The second man's partner was also taken in for questioning. Two people who came forward and indicated that they had been in contact with the perpetrator shortly before the events are also in custody. Police are investigating to establish the involvement of those in custody, authorities said.
Macron promised a swift response from the government on Friday.
"They will not divide us," he said. "This is what they are looking for and we must all stand together, citizens."
Minister of National Education Jean-Michel Blanquer reacted to the incident on Twitter Friday night.
"Tonight, it is the Republic that is under attack with the vile assassination of one of its servants, a professor," he said. "I think tonight of him, of his family. Our unity and firmness are the only answers to the monstrosity of Islamist terrorism. We will stand up."
Blanquer announced Saturday that there will be a national tribute to the teacher, including a minute of silence. "Samuel Paty embodied the Republic in its most noble form: its school," Blanquer said.
Eragny Mayor Thibault Humbert responded in an interview on local TV BFMTV Friday night.
"It is a very important emotion for us, for the inhabitants of our town," he said. "I want to have a thought for the family of this professor who was brutally murdered."
The offices of Charlie Hebdo underwent a terror attack in January 2015 that killed 12 people, including eight journalists from the satirical magazine. The trial for the attack is currently underway.
France's counterterror police opened an investigation after a stabbing attack in front of the former offices of Charlie Hebdo last month left two wounded.
Ricard acknowledged that prior incident on Saturday, saying, "This terrorist crime is the second committed during the trial of the January  attacks. ... This confirms the very high level of the Islamist terrorist threat that we have to face."
Charlie Hebdo expressed "horror and revolt" over the death of the teacher in a statement released on Twitter Friday: "We express our deepest support to his family, loved ones and all of the teachers. ... This foul act grieves our democracy but must make us more combative than ever to defend our Freedom."