(CNN) French officials on Thursday identified the second man who carried out this week's deadly attack on a Catholic church in northern France as Abdel-Malik Nabil Petitjean.

Authorities identified Petitjean, 19, from St.-Die-des-Voges, France, through DNA testing, the Paris prosecutor's office said.

He and Adel Kermiche, also 19, were killed by police after taking hostages Tuesday at a church in St.-Etienne-du-Rouvray in the Normandy region.

Petitjean, above, and an accomplice killed a priest in the name of ISIS, authorities say.

The two killed 86-year-old priest Jacques Hamel by stabbing him in the chest and slitting his throat, and took three nuns and two churchgoers hostage. Another person was stabbed in the hip and throat but is in a stable condition.

Kermiche was identified via fingerprints after the attack, which French President Francois Hollande called a "cowardly assassination" committed in the name of ISIS.

Both attackers known to authorities

A spokeswoman for Molins said Petitjean also was known to authorities and was on a list used to flag radicalized individuals considered a threat to national security.

Prosecutor Francois Molins revealed Wednesday that Kermiche had also been flagged as a radicalized Islamist and was under house arrest at the time of the attack. He was forced to wear an electronic monitoring tag after he traveled abroad to try to fight in Syria, Molins said.

Turkey had deported Kermiche in May 2015, a senior Turkish official told CNN on Thursday on condition of anonymity.

He had attempted to enter Istanbul last year but was sent back to Switzerland, where he had traveled from, and French authorities were alerted, the official said.

The 19-year-old was traveling with an identity card under the name of Kevin Kermiche.

"Upon examination by terror profilers stationed at the airport, Kermiche was denied entry and deported to Geneva," the official said.

Molins said Wednesday that Kermiche was found in Turkey traveling with a cousin's identity card and that the Swiss handed him over to French authorities.

Le Monde stops publishing attacker photos

The priest's killing follows a string of violent acts, some claimed by the Sunni terror group ISIS, including an attack in Nice on Bastille Day that killed 84 people.

The national French newspaper Le Monde responded to the recent violence by announcing it would no longer publish photos of assailants in terror attacks.

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"Since the emergence of terrorism by ISIS, Le Monde has evolved its practices many times. We notably decided not to publish propaganda images or claims by ISIS. Following the Nice attack, we have decided to no longer publish photographs of the killers, to eradicate the effects of posthumous glorification," the paper said in an editorial Wednesday called "Resisting the strategy of hate."

It said journalists were not exempt in the battle against hate and terrorism and that they should reflect on their practices, particularly in a changing digital landscape.

France has been under a state of emergency since the Paris terror attacks in November, and authorities have struggled to monitor thousands of domestic Islamic radicals on their radar.

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In response to the heightened terror threat, Hollande has vowed to double the number of officials charged with the task.