The incident happened on Tice Valley Boulevard near the Rossmoor Shopping Center around 11 p.m. Thursday.
Police found the man with significant injuries.
Witnesses told officers four people assaulted the man, robbed him and then drove off.
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Police later arrested two 18-year-old women, a 17-year-old girl and a 15-year-old girl.
Authorities say the adults were booked into Martinez Detention Facility and the juveniles were booked into juvenile hall.
Anyone with information can contact the tip line anonymously at 925-943-5865.
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