Police say a 14-year-old boy was knocked unconscious by a hit-and-run motorbike rider at a park in Mount Lawley.
He was rushed to Princess Margaret Hospital for treatment.
Around 3pm on Friday two boys were walking through Hamer Park when one of them was hit by the motorcycle.
The motorbike rider didn't stop to help the injured boy and instead rode off despite attempts by a member of the public to stop him.
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Police launched an investigation and a motorbike, believed to be the one which knocked down the teenager, was seized from a residence in North Perth.
A 12-year-old boy is being questioned.
Anyone with information is asked to contact Crime Stoppers.
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