In November, police released an image of a male motorcyclist they wanted to speak to in connection with the killings.
The French Gendarmerie released an artist's impression of a motorcyclist who was seen riding in the area shortly before the four murders took place.
The man's helmet was said by Mr Maillaud at the time to be "very particular" and one of only a few thousand models worldwide, with a bottom section which opened laterally to reveal the lower face.
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Two members of the public were injured along with two police officers who were in the unmarked vehicle.
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