The incident happened around 7 p.m. Saturday on Belle Harbor Circle.
Contra Costa Fire was dispatched to the scene just before 7:20 p.m.
Police have not released the victim's identity.
Authorities say the shooting appears to have been the result of a preceding physical altercation.
There is no word on any arrests.
Anyone with information is asked to contact Detective Elmore at (925) 252-4875.
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