PARIS » It took a text message from Syria to a mother in northeast France to reveal the identity of the third killer at the Bataclan concert venue in Paris: Your son died as a martyr Nov. 13.

For nearly four weeks, police had failed to identify the third gunman who stormed the concert venue along with two French Islamic extremists, killing nearly three-quarters of the total 130 people who died in the Paris attacks.

Then, about 10 days ago, Foued Mohamed-Aggad’s mother in Strasbourg received a text message in English announcing her son’s death “as a martyr” — a typical way that the Islamic State group notifies families of casualties. She gave French police a DNA sample which showed that one of her sons was killed inside the Bataclan, his brother’s lawyer said, confirming an account by French officials, who requested anonymity to release details of the investigation.

“Without the mother, there would have been nothing,” said the lawyer, Francoise Cotta.

The news announced today further confirms that the deadly Paris attacks were carried out largely, if not entirely, by Europeans trained by Islamic State extremists.

All the Nov. 13 attackers identified so far have been from France or Belgium, native French speakers who wanted to join IS extremists. The Bataclan attackers, who carried automatic weapons and wore suicide vests, were responsible for the worst of the carnage.

Mohamed-Aggad left Strasbourg for Syria in December 2013, a French judicial official said, at a time when about a dozen young men from the eastern French city headed to the war zone. Some returned of their own will — including his brother — telling investigators they were disgusted by what they had seen. Their suspected recruiter for IS, Mourad Fares, is also under arrest in France. All are charged with terror-related offenses and face trial.

Cotta said Mohamed-Aggad had told his family months ago that he was going to be a suicide bomber in Iraq and had no intention of returning to France. She told The Associated Press that Mohamed-Aggad was flagged as a radical but there was no warrant for his arrest.

“What kind of human being could do what he did?” his father, Said, told The Parisien newspaper. “If I had known he would do something like this, I would have killed him.”

The other two Bataclan attackers, Omar Ismail Mostefai and Samy Amimour, were also French. Two of the three gunmen detonated their explosives when police special forces moved in, while the third was shot by an officer and his explosives went off.

French-speaking Islamic State fighters, primarily from France and Belgium, tend to live and fight together. Mohamed-Aggad’s arrival in Syria coincides approximately with that of the two men who died with him inside the Bataclan, and with that of the suspected architect of the attacks, Abdelhamid Abaaoud, who was widely believed to be a leader of the francophone combat unit.

There is still identification work for the police to do. One of the Paris attackers, who was killed along with Abaaoud on Nov. 18 in a police raid on a hideout nearby, remains unidentified. Two of the suicide bombers at the French national stadium carried Syrian passports that are believed to be fake. France has released their photos in hopes of identifying them.

“What is important is that the investigation is progressing, that the accomplices are found out, that arrests happen,” French Prime Minister Manuel Valls said today.

“This will all take time. And in the face of the terrorist threat that is unfortunately here, we need to carry on with this work of tracking down terrorists because we are at war with radical Islam, with Daesh,” he said, using an Arabic acronym for the Islamic State group, which claimed responsibility for the attacks.

Attackers who struck Paris that night included three suicide bombers at the stadium, a squad who shot at bars and restaurants, a suicide bomber at a restaurant and the three gunmen at the Bataclan.

But the Bataclan was by far the deadliest attack. The three gunmen came in shooting, opening fire on the audience and the band, Eagles of Death Metal, according to police and witness accounts. Most of the victims were gunned down in the first few minutes, with a handful held hostage for nearly three hours, until the final police assault.