Daniel Gardner, 43, pleaded guilty Wednesday in Nashville to the Jan. 10, 2009, death of 34-year-old Marie Cogburn of Nashville.
Investigators say Gardner shot Cogburn in the back with a rifle during an argument then went to his mother's home to call police. Police say he returned to the scene of the shooting to wait for police and was arrested.
Gardner was a police officer in the 1990s for Murfreesboro.
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