"On behalf of the United States, I'd like to extend my really honest condolences to a friend of mine, President [Emmanuel] Macron of France, where they just yesterday had a vicious, vicious Islamic terrorist attack - beheading an innocent teacher near Paris", he said.
Police detained four close relatives of the attacker soon after the murder, with five more detained overnight, including the father of a pupil at Paty's school and an acquaintance of the pupil's father known to the intelligence services.
A suspected Islamic radical shot dead by police after the gruesome beheading of a history teacher in an attack near Paris was an 18-year-old of Chechen origin, officials said. During his standoff with the police, he had been armed with a knife and air-soft gun, which fired plastic pellets.
"A civilization does not kill an innocent person, barbarism does", Tareq Oubrou, imam of a mosque in Bordeaux, told France Inter on Saturday.
The prosecutor said a text claiming responsibility and a photograph of the victim were found on the suspect's phone.
On Saturday, anti-terror prosecutor Jean-Francois Ricard said Mr Paty had been the target of online threats for showing the cartoons to his civics class.
On Saturday morning, floral tributes were laid outside the College Bois d'Aulne, where Samuel had taught.
Between bursts of applause, others recited: "Freedom of expression, freedom to teach".
The history and geography teacher, 47-year-old Samuel Paty, had previously received death threats for showing Prophet Mohammed cartoons during a lesson on freedom of expression.
The teacher made the decision to show the controversial images when discussing the 2015 Charlie Hebdo attacks, in which two al-Qaeda gunmen killed 12 and injured 11 employees of the satirical magazine after it had continued to depict the Prophet Mohammed in various cartoons.
"We said to the teacher it was not good to show photos like this and that it would cause a huge problem", Lusiela said.
Ricard did not say if the attacker had any links to the school, pupils or parents, or had acted independently in response to the online campaign.
Education Minister Jean-Michel Blanquer described the attack as a "despicable assassination of one of its servants, a teacher", and said his thoughts were with the family of the victim. You will not divide us.
France has the largest Muslim population in Western Europe with up to 5 million members, and Islam is the country's second-most popular religion.
Part of that population is made up of Chechens.
Chechnya is a predominantly Muslim Russian republic in the North Caucasus. The outlet published caricatures of the Prophet Muhammad, unleashing divisions that are still casting a pall over French society.
The controversy of the cartoons was revived last month when Charlie Hebdo chose to re-publish them to coincide with the start of the trial of accomplices in the 2015 attack.
Some carried placards stating: "I am a teacher" and "I am Samuel" - echoing the "I am Charlie" cry that travelled around the world after the 2015 Charlie Hebdo killings. Prior to the said attack, the magazine's offices were struck by a gasoline bomb in 2011.
He further called for French government to not hold Islam and Muslims accountable for a "criminal act by an extremist", and to enforce hate speech laws to prevent the spread of hate speech against Muslims.