PARIS (AP) — French President Emmanuel Macron denounced what he called an “Islamist terrorist attack” against a history teacher decapitated in a Paris suburb Friday, urging the nation to stand united against extremism.

The teacher had discussed caricatures of Islam's Prophet Muhammad with his class, authorities said. The suspected attacker was shot to death by police after Friday’s beheading.

The French anti-terrorism prosecutor opened an investigation concerning murder with a suspected terrorist motive, the prosecutor’s office said.

Macron visited the school where the teacher worked in the town of Conflans-Saint-Honorine and met with staff after the slaying. An Associated Press reporter saw three ambulances arrive at the scene, and heavily armed police surrounding the area and police vans lining leafy nearby streets.

“One of our compatriots was murdered today because he taught ... the freedom of expression, the freedom to believe or not believe,” Macron said.

He said the attack shouldn’t divide France because that’s what the extremists want. “We must stand all together as citizens,” he said.

The gruesome killing of the teacher occurred in the town of Conflans-Sainte-Honorine while the suspect was killed by police in adjoining Eragny.

A police official said the suspect, armed with a knife and an airsoft gun — which fires plastic pellets — was shot dead about 600 meters (yards) from where the male teacher was killed after he failed to respond to orders to put down his arms, and acted in a threatening manner.

The teacher had received threats after opening a discussion “for a debate” about the caricatures about 10 days ago, the police official told The Associated Press. The parent of a student had filed a complaint against the teacher, another police official said, adding that the suspected killer did not have a child at the school. The suspect's identity was not made public.

The suspect’s identity was not made public. French media reported that the suspect was an 18-year-old Chechen, born in Moscow. That information could not be immediately confirmed.

The two officials could not be named because they were not authorized to discuss ongoing investigations.

“We didn't see this coming,” Conflans resident Remi Tell said on CNews TV station. He described the town as peaceful.

It was the second terrorism-related incident since the opening of an ongoing trial on the newsroom massacre in Jan. 2015 at the satirical newspaper Charlie Hebdo after the publication of caricatures of the prophet of Islam.

As the trial opened, the paper republished caricatures of the prophet to underscore the right of freedom of expression. Exactly three weeks ago, a young man from Pakistan was arrested after stabbing, outside the newspaper’s former offices, two people who suffered non life-threatening injuries. The 18-year-old told police he was upset about the publication of the caricatures.

The incident came as Macron's government is working on a bill to address Islamist radicals who authorities claim are creating a parallel society outside the values of the French Republic.

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Michel Euler in Conflans-Saint-Honorine and Nicolas Vaux-Montagny in Lyon contributed to this report.