By Hugh Schofield
BBC News, Paris
The killings have sent shockwaves through the city of Nantes
France has been transfixed by an appalling human drama - the murder of a mother and four teenagers, shot dead in chillingly clinical fashion, seemingly by the children's father.
Part of what makes the story so compelling is the prosperous, apparently happy, provincial setting in which it took place.
There is also the fact that the presumed killer - Xavier Dupont de Ligonnes - is still at large three weeks after the murders.
Murders happen all the time, but now and then there are murders that, by their extraordinary circumstances, by the eccentric character of their perpetrator, or by the social context in which they are set, somehow command our attention in a different way.
Such is the case of the bizarre, terrible tale of Xavier Dupont de Ligonnes - France's most wanted man.
Strict Catholic upbringing
As his name suggests (the "de" is the clue) Xavier Dupont de Ligonnes comes from old French nobility.
His ancestors lived in a southern province called the Rouergue and included a sister of the 19th Century poet Lamartine.
Agnes and Xavier Dupont de Ligonnes seemed a perfectly happy couple
Xavier was born 50 years ago in Versailles, and typically for the place was given a strict Catholic upbringing.
He married a young woman whom he had met in Versailles called Agnes. They had four children - Arthur, who was 20 and a student; Thomas, 18, a gifted musician; Anne, 16, and Benoit, 13, who were both still at school.
They settled in Nantes, the city at the mouth of the river Loire which in recent years has become a thriving economic hub. Thousands of families have moved there from Paris because of its agreeable provincial lifestyle.
The Dupont de Ligonnes lived in a smart townhouse. They had three cars. The younger children attended a Catholic school and Benoit was a choirboy at the church. Agnes taught catechism.
Photographs show an attractive, happy family. There is a particularly poignant one of Xavier holding his daughter Anne. They are looking at the camera and she is giggling.
This is a natural, properly functioning home where people love each other and things always work out in the end. Not a hint of the lurking psychological darkness.
Last December, Xavier Dupont de Ligonnes began attending a shooting club outside Nantes.
He told the club's owner that he had inherited a rifle from his father who had recently died and he wanted to learn how to use it.
He attended regularly, sometimes taking along two of his sons. The owner said they seemed totally normal. He said he had lunch with the family one day and the parents laughed together and held hands.
At the start of April, Xavier went to the club to practise four days in a row. He also bought a silencer.
At about this time he bought some other items too - sacking, cleaning fluid, chalk lime, a spade and a two-wheel trolley.
On Sunday 3 April he took the family out for a dinner in Nantes - again all seemed normal.
Mistress and debts
But it was probably on the next night, Monday, that the plan was put into effect.
The two younger children were still at school
With the .22 rifle and the silencer, the family were shot dead one by one, probably as they slept. The two family Labradors were also shot.
The bodies were buried under the terrace and Xavier Dupont de Ligonnes disappeared.
France has been, quite naturally, riveted.
Since the bodies were found two weeks ago, we have learned more about Xavier Dupont de Ligonnes, whose handsome if bland features look out from every news stand.
It appeared he had planned an abrupt departure - writing to the children's schools to say that the family was emigrating.
His financial situation was catastrophic. He had various internet-related businesses and they were failing.
He had spent his wife's inheritance and had borrowed money from a lover in Paris, who was now demanding it back.
Crisis of faith
We also know he had had a complex relation with his late father, whom he hero-worshipped.
The family were shot dead, one by one
His Catholic faith was also in crisis. He had shared his doubts on a Roman Catholic internet chat site, and if you wanted to, you could read his religious ramblings online.
Above all - where is he? He was seen in southern France in the days after the killings, but since then nothing.
It is not just the horrific human element that makes it all so gripping.
Somehow it seems a very French murder story, something to do with the provincial setting and with the times we live in.
It is the tale of an upper-middle-class French family caught at a juncture between a prosperous, reassuring past and an uncertain, unsettling future.
At the centre of the story is a man who fails to find his way in this changing world and apparently makes his own wife and children pay the price.
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