Detectives are investigating after three people, who appeared to be British holidaymakers, were shot dead in a car in the French Alps. Here is what we know so far, and the questions police will attempt to answer.
What happened in the hours leading up to the attack?
The family were holidaying in an area called Saint Jorioz. They had arrived on Monday and were due to leave by the end of the week.
It is believed neighbours at the site alerted police when they appeared to be missing.
Police will interview these campers and caravanners in an attempt to get as much information as possible about what happened in the hours before the attack.
They will want to know what time the family left the site, what they did beforehand, what time they were expected back at the site, and who was in the car when they left.
Reports suggest the front passenger seat was empty when the car was discovered – police will attempt to establish whether the seat was empty for the duration of the journey.
CCTV in the area will be checked to find out where the car travelled to after leaving the site.
Establishing and tracing all people and vehicles close to the crime scene at the time of the attack will also be important, to collate eyewitness testimony.
Who was the cyclist and why was he shot?
A cyclist was found dead nearby. Police will attempt to establish where he was a travelling from and to, and whether he was shot before or after the victims in the car.
He is understood to be a factory worker from nearby Ugine, but his name and age has not been officially confirmed.
A key plank of the investigation will be to find out whether the family in the car were targeted, and if so, why a passer-by was also killed.
What happened in hours following the attack?
A British cyclist, who is a former member of the RAF, discovered the victims just moments after the attack happened, prosecutors have said.
Shortly before the discovery he was overtaken by the cyclist who was later found dead at the scene.
On arriving, the eight-year-old girl collapsed in front of him. He placed her on her side in the recovery position and called the emergency services.
According to police, he noticed the engine in the car was still running, and smashed a window to turn off the engine.
One witness is reported to have spotted a car driving very fast away from the scene around the time of the shooting.
The killings took place at 4pm local time, and we know that the four-year-old girl who survived was discovered underneath two bodies almost eight hours later.
It is unclear how long police were at the scene before the youngster was found.
Another girl, aged eight, was found near the car with gunshot wounds. We don't know how long she was alone outside the car, what she did during that time, or at what time she left the vehicle.
Are there any theories on a possible motive?
Detectives have remained tight-lipped so far. However AA president Edmund King said French gangs are known to prey on tourists.
He said: "They are, quite frankly, bandits, and they target visitors from the UK. There have been incidents in the south of France and in places around Lyon. They look for UK-registered cars then they flash their lights and perhaps point at the tourist car's wheels.
"The tourists stop their car and while one gang member distracts them, another steals from their car."
Police have stated that the shootings looked "professional", however they have not elaborated whether they are pursuing a different line of inquiry.
Have the victims been identified?
The British husband and wife killed were named by neighbours as Saad and Iqbal al Hilli.
Their two children, who survived the bloody attack, were named as eight-year-old Zehab and four-year-old Zaina.
A Swedish passport has been found on the eldest woman, according to police.
What type of weapon was used?
Dozens of shell casings were found close to the car, and detectives will be working to establish the type of gun used, as well as whether there was more than one weapon used.
This could help to establish whether more than one person was involved in the shooting.
Once the gun has been identified, police will attempt to trace any registered owner of the weapon.
No weapons have been found at the scene, and a search with dogs is ongoing.
What will the post-mortems focus on?
Discovering whether a struggle took place ahead of their deaths could be crucial in piecing together the circumstances surrounding the killings.
Post-mortems results are due to be released on Friday. However police have confirmed that three of the four people killed were shot in the head.
Were any gunshots heard locally at the time of the shooting?
No, according to police.
Have the surviving two children given police any information?
The eight-year-old is currently in an induced coma, however the younger girl has apparently spoken about the killings. She has said that she heard a lot of noise, and was scared.