He said he told her he planned to file for divorce, and she threatened to kill herself. He said he then went for a drive, making at least three stops before returning home and finding her body, according to the grand jury report.
The new investigation turned up contradictions in his story, according to prosecutors, including a neighbor who said his car was in the driveway when she heard a single gunshot.
State police said Walker did not attempt to render aid to his dead wife or check her for vital signs, and that he called the home of a police dispatcher upon discovering her body, rather than dialing 911. His gun was on the bed by her side.
A trooper interviewed Walker in March 2010.
"Throughout his interview, Walker never expressed any remorse that he had left Lynda alone," the grand jury wrote. "Walker failed to deny that he had killed his wife until he was walking out the door of the barracks to leave."
April Harvey told the grand jury she and Walker had been having a sexual relationship at the time of the shooting - they subsequently were married for 19 years and have three children together.
Harvey testified Walker came to the McDonald's restaurant where she worked the night of the shooting and told her they had argued, and he was afraid. Walker did not disclose that encounter to investigators in 1983, the grand jury said.
Harvey told jurors, according to the investigative report, that Walker said police had "no evidence as he obtained the evidence police seized from the scene many years ago. Walker told Harvey that he destroyed some of the evidence by burning it. Walker also sold the .45-caliber pistol."
After a complete autopsy was performed on Lynda Walker in May 2011, a forensic pathologist determined she died of a gunshot wound from close distance, with the bullet entering her chest and exiting her back. Her death was deemed a homicide.
John Walker was suspended without pay Wednesday from his job as a part-time sergeant with the Montrose Borough police department. He also works part-time for police in Silver Lake Township, but the chief there said Wednesday he was just learning of Walker's arrest.
Both Montrose and Silver Lake Township are in Susquehanna County, north of Scranton and just south of the New York state line. In 1983, Walker was a police officer in Great Bend, also in Susquehanna County. He has also worked as police officer in Clarks Summit, and as a military police officer in the Army.