French police on Tuesday arrested a 48-year-old man, described by a source as a former cop, over the 2012 killings of a British-Iraqi family and a cyclist, in their first breakthrough in the case.
Checks on the man's phone "put him in the zone at the moment" of the murders of the al-Hilli family and the cyclist on September 5, 2012, another source said.
He said several arms were seized at a raid in the man's home following his arrest and revealed his passion for guns. Another raid was carried out on a house in the nearby village of Lathuile.
Ballistic tests will be carried out to determine if these weapons had been used.
Annecy prosecutor Eric Maillaud said the man, from the Haute-Savoie region, was placed in formal custody and detained following the release in November of a police sketch (See below) of a mysterious motorcyclist seen near where the quadruple murder took place.
"This arrest, which may not be the only one, was the result of witness statements" that came in after the image was released, Maillaud said.
A source close to the case said the man, a father of three, was a former policeman from the town of Menthon-Saint-Bernard.
"The man, if it is indeed the same person we think, was dismissed in June" from the force, Antoine de Menthon, the mayor of the town of Menthon-Saint-Bernard told AFP.
The man is being kept in custody and French officers carried out a search of his home in the presence of his girlfriend.
The arrested man's home village of Lathuile was in the news in November after the owner of a camping site was shot dead at her home by two men wearing hoods.
Prosecutors at the time did not link the murder to the 2012 killings.
Earlier in the day one source close to the investigation told AFP the suspect was a "taciturn mountain man" and a gun enthusiast who "lives on the fringes of society".
Saad al-Hilli, 50, his wife Iqbal, 47, from Surrey and grandmother Suhaila al-Allaf, 74, who lived in Sweden, were all gunned down in their car on September 5th on a quiet road not far from the town of Annecy.
French cyclist Sylvain Mollier, 45, was also killed nearby. The al-Hilli's two daughters – seven-year-old Zeinab, and four-year-old Zeena – survived the attack.
Prosecutor Maillaud said there was no apparent "direct link" between the suspect and the victims.
It was the police sketch, seen below, of the mysterious motocyclist seen near the scene of the murders that led to the suspect being arrested on Tuesday.
Witnesses gave a description to police of the motorcyclist early on in the case, but his e-portrait was not immediately released by police for fear he would go into hiding.
Investigators had hoped that the helmet depicted in the sketch would prove a fruitful avenue of inquiry, since it is a rare model, used by French police during the 2000s, with only 8,000 made in black, as seen by witnesses.
But despite receiving around 100 calls from the public, not one had led to any kind of break in the probe.
However sources close to the investigation told AFP that Tuesday's arrest could prove significant.
The source close to the case said the arrest was "an important step forward in the investigation" but added that "other arrests should follow."
French police can hold suspects in criminal cases for up to 48 hours without charge.
The source was cautious about the arrest, noting the lack of any links to the victims.
"This is someone who lives around Chevaline and who has no known employment," the source said. "He was someone that investigators were looking at as part of their local leads."
The killings has so far baffled investigators despite major efforts on both sidesof the English Channel.
The main suspect in the probe had be Saad al Hilli's broter Zaid, with police suspectign that a family fued over inheritance may have been the motive behind the mursders.
Zaid was arrested and placed on bail but in January this year British police announced that he would be released as there was not enough evidence to bring charges.
The brother admitted he and his Saad had been involved in a bitter dispute over inheritance but insisted he was innocent of orchestrating the murders.
"The French, I don't trust them at all," he told The Times newspaper last year.
"My brother was killed there in that region and I am not going to take the risk."
In an interview with The Local earlier this year, Annecy prosecutor Eric Maillaud admitted their manhunt may never track down the murderers, but it was still too early to know.
“Of course it is possible we will never find them, but it’s too early to conclude that,” Maillaud said, back in March. “The investigation is only six months old, which in terms of police inquiries is a very short period of time.”