(Portland, OR)  --  Police are confirming they've discovered the bodies of a missing Salem woman and her 3-year-old son.  The Oregon State Medical Examiner says search crews found the bodies of 25-year-old Karissa Fretwell and her son Billy Fretwell Saturday in a remote wooded area of Yamhill County.  Police say Karissa died from a single gunshot wound to the head.  Investigators are still looking into how Billy died.  Police arrested Billy's biological father, 52-year-old Michael Wolfe, late last month.  Wolfe was indicted last week on charges of kidnapping and murdering the two.