London (CNN) -- A British girl who survived the execution-style killing of her father, mother and grandmother in a normally idyllic region of the Alps last week returned to Britain on Friday, authorities said. Zainab al-Hilli, 7, left France in the morning and arrived in the UK, Surrey police said. As the only survivor, she could be a key witness who saw who carried out the shooting, according to the French prosecutor leading the investigation. She spent several days in a medically induced coma, and as of Wednesday, she remained too badly injured to be questioned, Eric Maillaud said. She was beaten and shot in the attack, and rescued by a British cyclist who came upon the scene on September 5.
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The 7-year-old girl is potentially the only person now alive who saw the killings, authorities say
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A French prosecutor and judge are in Britain seeking new leads in the case
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A British cyclist who was first at the scene of the shootings recounts what he saw
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Saad al-Hilli, his wife and mother-in-law were shot dead, along with a French cyclist
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He managed to flag down a car and asked the @placeholder motorist to call for help, before returning to the scene to check on the girl, who was then unconscious.
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He added that he was not surprised that @placeholder police had failed to spot a second child, a 4-year-old girl, hiding in the back of the car under her dead mother's legs, for nearly eight hours.