A 41-year-old local man, believed to be the driver of the car, was arrested for grievous bodily harm at the time.
This is now being treated as a homicide investigation by Surrey and Sussex Major Crime Team working in conjunction with colleagues in West Sussex Division.
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A serious case review into the exploitation of young people in Oxford has documented a catalogue of failures by police and social services.
Oxfordshire Safeguarding Children's Board has apologised over the time it took to investigate child exploitation in the county.
Tuesday's weather for the west of the region