Washington County Prosecutor John Threet filed the charges Tuesday afternoon against 27-year-old Mandrake Patterson.
Patterson will appear in court on Wednesday to face two counts of capital murder and one count of attempted capital murder.
Police say Patterson shot and killed his wife, Hope Patterson, and his mother-in-law, Betty Desalvo, last January.
Officers say he also shot and injured Denise Fulfer, Desalvo's sister.
Patterson is in the Washington County Jail on no bond.