Dec. 15, 2009 -- Ty Hansen believes he knows the real story behind his mother's disappearance nearly 50 years ago.
Hansen believes Joan Hansen didn't run away from her family when he was just 2 years old, but was killed by his father because she had filed for divorce.
To prove his case, Hansen is suing his father for damages -- despite the fact that Robert Hansen is dead.
Hansen insists he just wants the truth of his mother's disappearance to finally be heard and his father's culpability to be legally settled. He acknowledges, however, there are several million dollars at stake.
"I want justice for my mother. I want her story to be told," Hansen told ABCNews.com. "I don't want this to be swept under the rug like it has been for the last 47 years."
Hansen says he was raised by his father telling him and his two siblings that his mother had deserted the family, but a very different story emerged when he began researching his mother's story 15 years ago.
What Hansen found was divorce papers that indicated violence between his parents, and the fact that his mother was reported missing when she didn't show up for a hearing regarding the separation. In addition, his mother's friends who knew her at the time of her disappearance said she had vowed she'd never desert her kids.
Patricia Martin, one of Joan Hansen's best friends, claims she spoke to Joan Hansen moments before she was murdered.
"We were speaking on the phone and all of sudden Joan said 'Oh my God,' then there was silence and then I heard her holler 'Don't!'" said Martin, 76. "She kept saying 'he's coming' and then she started screaming and the phone went dead."
"I have no doubt what happened to Joan," said Martin. "I know he killed her."
Son Confronts Dad, Calls Him 'A Killer'
Hansen said that no matter whom he talked to – his father's friends, his mother's lawyer and even aunts he never knew existed – everyone told him the same story.
"They all say, well your dad killed your mom and he probably buried her down there at the barn site," said Hansen, who is now 50 and living in Costa Mesa, Calif., where he works as a self-employed house painter.
King County Sheriff's office spokesman Sgt. John Urquhart told ABCNews.com that Robert Hansen has always been and will continue to be a "person of interest" in his wife's case, even now that he's deceased.
"She's gone, she's disappeared, and we believe she's been a victim of a homicide," said Urquhart. "We've been investigating him for years and years, a long, long time."
"We've jack-hammered road, we've dug areas up and jack-hammered again," he said.
Urquhart said Robert Hansen was never arrested because there was never enough "probable cause" to do so.
Hansen believes that his mother was buried in the days following her Aug. 8, 1962 disappearance underneath a cement slab in the family barn, but that the area has since been paved over by a major state highway.
Despite employing cadaver dogs, ground-penetrating radars and even convincing the King's County Sheriff's office to excavate a portion of the road, his mother's body has never been discovered.
While Hansen continued on his search for the truth about his mother, he says his father became increasingly estranged from him, eventually wanting "nothing to do" with his son. It culminated with the father writing Ty Hansen out of his will and leaving his estate to a "friend in Costa Rica," according to ABC's Seattle affiliate KOMO.
When Hansen confronted his father about his mother, his father never denied the murder but would never talk about her disappearance either.
"My dad knew I was investigating, but he never reached out to say 'stop.' He just basically told me to go to hell," said Hansen. "I went to his house several times in 2005 and 2006 while I was traveling to do more legwork on the project and I'd visit him and confront him and tell him I thought he was a murderer."
"I'd say to him, 'Dad, I think you killed mom. I think you're a liar, a murderer and a coward,' and he'd just cuss at me, and tell me to get off his property," said Hansen.
Then, in August of this year, Hansen got a phone call from the King's County coroner's office to tell him that his father had committed suicide, asphyxiating himself in his car in his garage.
Hansen explains his father's suicide as the result of a combination of factors including the tightening noose of the investigation into his mom's disappearance, a recent divorce from a woman he married later in life, and his old age. He was 84 when he died.
"I think that the prospects didn't seem very good to him, so he decided he was done with it," said Hansen.
Hansen also found tax records that suggested his father had nearly $5 million to his name, earnings from property he owned as well as his years as a successful landlord.
Robert Hansen Remains 'Person of Interest' in Mom's Disappearance
As for the investigation back in the 1960s when Joan Hansen disappeared, Urquhart was obviously not working for the Sheriff's office.
The man who was sheriff at the time, Ted Forrestor, was unable to be reached by ABCNews.com, but Hansen claims that Forrestor's long term relationship with his father – they had grown up together – and the fact that case was only ever looked at as domestic dispute, led to the inconclusive investigation.
At the time, Kent, Wash., only had about 9,000 residents, and the fact that "everyone knew each other" tarnished the investigation, said Hansen.
Repeated calls made to Forrestor's Washington-area home were not returned.
The complaint for wrongful death and personal injuries filed by Hansen in King County Superior Court in November has not yet been answered by Robert Kitto, the executor of his father's estate.
Kitto, reached by telephone by ABCNews.com, declined to comment on the worth of Robert Hansen but said that he does not know anything about his client, whom he has worked with for nearly 40 years, that "would suggest he would harm his wife."
The amount of monetary damages that Hansen will seek will not be determined until trial, which has not yet been scheduled.
Hansen says that while he's aware critics are accusing him of trying to pilfer money from his dead father, he doesn't care. All he wants, he says, is justice for his mother.
"I don't care what the critics say," he said. "It doesn't bother me one single bit whether I get nothing or everything makes no difference. I'm still going to pursue the story and I still want justice."