WHO IS PARIS ATTACKER?

Who is Paris attacker Ismael Omar Mostefai?

he quiet of this bucolic French town, known for centuries for its historic and majestic medieval cathedral, has been shattered by the discovery that a former resident helped carry out one of theworst terrorist attacks in French history.

Ismael Omar Mostefai, 29, lived here quietly for years, before he was identified as one of the attackers whobrutally massacred dozens of Paris concertgoers with a Kalashnikov before blowing himself in the crowd with a suicide bomber's vest.

Mostefai, Parisians learned, was identified through a gruesome find. He was literally "fingered" by a fingerprint, pulled from a severed finger, found in the carnage of body parts in the concert hall, according to investigators.

The Bataclan massacre, as it is now known, was just one wave of the eight terrorist strikes across Paris on Friday night, bringing horror and darkness to the fabled city.

The moment the shots rang out at the concert hall 01:09

The series of terrorist attacks left at least 129 dead and scores more wounded, many of them still in critical condition.

Perhaps as shocking as the crimes committed was where Mostefai had been a resident. Far from being any sort of poor or impoverished area, Chartres is a scenic tourist spot, with narrow cobbled streets and stunning vistas. It is about 50 miles southwest of Paris.

Even in the neighborhood where Mostefai lived, just 10 minutes from the center of town in the La Madeleine area, the streets are quiet and tree-lined, with clean streets and sidewalks.

People in Chartres wonder: Why here?

So how did Mostefai, previously unknown to the general public, become radicalized to do such a thing?

"Yes, that is what shocks people," said Mayor Jean-Pierre Gorges, who was the first person to publicly identify Mostefai, by name, in a Facebook entry late Saturday. The mayor is a member of Parliament and is a well-known figure in the region.

"We have someone who was radicalized in a town that's practically the capital in France of Catholicism -- and, you saw the cathedral, one of the world's greatest historic monuments."

Francois Molins, the lead French prosecutor in the investigation, said the assailant "was identified thanks to his finger, and fingerprints." He said Mostefai, however, had been known to authorities as a possible threat.

Molins said in a press conference that Mostefai had an "S" file on him for years, which means investigators believe he had been "radicalized" in some way, though it was not clear whether he would act on his radicalization.

Surveillance files have been opened on more than 5,000 suspected Islamic extremists in France, but security services only have the manpower and resources to monitor a small fraction of these numbers 24/7. About 1,000 have traveled to Syria and Iraq to fight jihad or are in transit there -- and those are just the ones French authorities know about.

Gorges said in an interview with CNN on Sunday that he decided to reveal Mostefai's identity publicly after a briefing by investigators.