Step one: bike drives into police station.
Step two: man gets off bike, is arrested.
According to Guangxi News Network, the suspect snatched a woman's purse in a town near Beihai on 12 April.
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The 29-year-old biker heard about the theft and followed the suspect into a parking lot, where he offered him a ride. Upon arrival at the station he quickly warned the policemen, who closed the gates on the culprit.