(CNN) -- It's been 31 years since Stanley Guidroz first reported his 3-year-old son missing in Tacoma, Washington. 

Investigators, after reopening the cold case, now say the boy, Wallace Guidroz, was never missing at all and that his father had killed him. 

Guidroz, 57, has been charged with first-degree manslaughter after he confessed to the crime, said Pierce County Prosecutor Mark Lindquist on Tuesday. 

"This is another success for the Cold Case Unit," said Lindquist. "Justice matters, no matter how long it takes." 

Guidroz first reported his son missing in January 1983, telling Tacoma police that his son had gone missing in a neighborhood park after they had gone fishing together. Guidroz said he believed that a family they had met in the park had kidnapped him, prosecutors said. 

Police were unable to locate a family that fit the description Guidroz gave them, and they were unable to connect Guidroz to the boy's disappearance. 

For years, the mystery of what happened to Wallace remained unsolved. 

Guidroz left Washington state in 1984 and did not return, according to a press release from the Pierce County Prosecutor's Office. 

In 2011, Cold Case Unit Detective Gene Miller reopened the case. Miller reviewed old documents from the initial investigation and saw that Guidroz's stories never seemed to add up. 

There were "several inconsistencies in Guidroz's account of the events from the day Wallace went missing," the release said. 

Guidroz resurfaced in Louisiana in March 2011 after reports that he had been charged in the killing of his wife, who is not the mother of Wallace. 
Who is the father in this story?
Who is his son?
How old was he when he was reported lost?
what he really lost?
WHat actually happened to him?
How do we know?
How old is the dad now?
What are teh charges against him?
Where did he originally tell the police his child was lost?
Where were they supposed to be in Tacoma?
What were they doing there?
Did he ever move?
When?
when was the case reopened?
By who?
Where did they eventually find the father?
What were the charges against him there?
was she the mom?
Stanley Guidroz
Stanley Guidroz first reported his 3-year-old son
Wallace Guidroz
 the boy, Wallace Guidroz
three
reported his 3-year-old son
no
Wallace Guidroz, was never missing at all
his father killed him
 his father had killed him
the Prosecutor said
 said Pierce County Prosecutor Mark Lindquist on Tuesday. 
57
Guidroz, 57
first-degree manslaughter
Guidroz, 57, has been charged with first-degree manslaughter
Tacoma, Washington.
 reported his 3-year-old son missing in Tacoma, Washington. 
a neighborhood park
 telling Tacoma police that his son had gone missing in a neighborhood park after they had gone fishing together.
fishing
 in a neighborhood park after they had gone fishing together
yes
Guidroz left Washington state in 1984 and did not return
1984
Guidroz left Washington state in 1984
In 2011
In 2011, Cold Case Unit Detective Gene Miller reopened the case
Gene Miller
Cold Case Unit Detective Gene Miller reopened the case
Louisiana
Guidroz resurfaced in Louisiana
killing his wife
he had been charged in the killing of his wife, who is not the mother of Wallace.
no
 who is not the mother of Wallace