A man who three years ago drove across south Louisiana with his wife’s body in the back seat of his car now faces charges in another killing — the disappearance of his 2-year-old son in Tacoma, Washington, more than 30 years ago.

Stanley Guidroz, 57, who has been serving time at the Louisiana State Penitentiary at Angola for his wife’s murder, now faces a first-degree manslaughter charge in the 1983 death of his son Wallace Guidroz, whose body has never been found.

The Tacoma prosecutor’s arrest warrant, issued this week, represents a possible ending to a case that has gone unsolved for decades, and marks three years of steady effort by a Tacoma cold-case detective to uncover what happened to the missing 2-year-old, nicknamed “Wally.”

Guidroz has been in jail since March 2011, when he told police he stabbed his wife at a Burger King in Houma after an argument, then drove around for hours before stopping at police headquarters in Zachary with her body in his car. The officers found Pepettra Guidroz lying dead below the 1999 Ford Mustang’s back seats.

For Gene Miller, Tacoma Police Department’s cold case detective, Guidroz’ arrest in Louisiana was an opportunity to question him about events across the country from nearly three decades ago. Miller met with Guidroz a few weeks after his arrest, but was not expecting what followed — a detailed confession, complete with a description of where Wally had been buried.

“I personally believe he’s carried some guilt with him for a lot of years over this,” Miller said.

Guidroz initially told police that on Jan. 10, 1983, he had been fishing with his son at Point Defiance Park by Tacoma’s shoreline when the boy wanted to look at some ducks in a pond, Miller said. They ran into another family, Guidroz had claimed, and then Guidroz wandered off, leaving his son behind.

When Guidroz returned, his son was gone. Guidroz claimed he then looked for more than two hours before alerting police.

Police could never find that family, but they also weren’t able to pin Guidroz to the child’s disappearance. But Miller, looking back at the account, noticed “common sense” flaws in Guidroz’ story, and said that “it just seemed very, very improbable that it could have happened the way he said.”

Miller said weather reports from Jan. 10, 1983, show rainy conditions at the park, with sunset minutes away — far from an ideal time to yield to the child’s request.

Years later, Miller spent more than eight hours speaking with Guidroz across three visits in prison, first in Terrebonne Parish and later at Angola. Guidroz told Miller the fishing trip did happen, but after he and the boy returned home and Wally was misbehaving in his highchair, Guidroz “just lost it,” said Heather Songer, a spokeswoman for the Pierce County Prosecuting Attorney’s Office, in a news release. Guidroz dealt the child a back-handed blow that sent him to the floor, hitting his head. The child remained motionless after that, and Guidroz was sure then he was dead, according to the release.

Guidroz buried the boy in a shallow grave by the Tacoma waterfront, then called police to say his child was missing and that a family he had seen at the park had kidnapped him, Songer said.

She added that Guidroz was nervous in his retelling of the story, since he did not want to be known as a “child killer” at Angola.

One year after the boy’s death, Guidroz left Washington for Louisiana. He separated from Wally’s mother soon after the incident and eventually married the woman he later admitted to killing.

Guidroz grew up near Terrebonne Parish and still has family there as well as in Lafourche Parish; military service was what brought him to Washington state. Miller would not describe how Guidroz made a living over three decades, except to say that his work was “sketchy” and inconsistent.

With a confession in hand, Tacoma police still had plenty of work to do. They turned up ground around the area of shoreline that Guidroz described, all while deploying cadaver dogs and radar equipment. But investigators have yet to the find the body. Part of the problem might be that the burial spot Guidroz described became part of a public park three years after the incident, and it’s possible land was moved or upturned in the process.

But Miller thinks the body is still buried somewhere in that area.

Guidroz will be transported to Tacoma for arraignment, likely by U.S. Marshals, and once there he will remain imprisoned in Pierce County Detention and Corrections Centeruntil a verdict is delivered, said Officer Loretta Cool, a Tacoma Police spokeswoman. If found guilty, it is unclear whether Guidroz would serve the rest of his time at Angola or at a jail in Washington. That would depend on factors such as which killing brought more jail time, Cool added.

Meanwhile, the search for Wallace’s body continues. For Miller, the case doesn’t truly feel over.

“Quite frankly I’m not satisfied only because I haven’t been able to find Wally and give him a proper burial,” Miller said.