Forty years ago, a 6-year-old boy in a cowboy hat asked Gary Ridgway a question:
"Why did you kill me?"
Blood streamed from a stab wound in the boy's side and ran into his cowboy boots.
Ridgway, a teenager then, did not answer immediately. He stood with the knife in his hand and laughed. Then he wiped both sides of the blade on the boy's shirt.
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"I always wanted to know what it felt like to kill somebody," he said.
Years later, the boy remembered Ridgway walking away, "kinda puttin' his head in the air, you know, and laughin' real loud."
The boy survived. He spent several weeks in the hospital. The incision to repair his liver was about a foot long.
Eventually he moved from King County to California. A King County sheriff's detective found him there earlier this year.
The story of the stabbing appears in the 133-page summary of evidence submitted Wednesday by King County prosecutors, underlining Ridgway's admission to 48 murders, unmasking the Green River Killer.
Decades after the stabbing, the boy's question echoes across the years, in the voices of the families of Ridgway's victims.
Why did Ridgway kill? In the prosecutor's summary, investigators openly say they have no answer. During a news conference Thursday, Sheriff Dave Reichert, who chased Ridgway for 21 years, heard the same question, and replied the only way he could:
"Because he wanted to," Reichert said.
During one of Ridgway's many interviews with investigators and prosecutors over the past several months, a forensic psychologist asked whether something was missing in him that was present in other people.
"Caring," the killer replied.
Ridgway told investigators he never thought about how victims felt while he was killing them. He did not want to see their faces. To him, they were not people.
Investigators trying to retrace his murderous steps after 20 years showed him photographs of victims. Generally Ridgway claimed not to recognize them.
"The women's faces don't ... mean anything to me," he said.
Ridgway's profound lack of empathy for others fits the definition of a psychopath, said Dr. Peter Roy-Byrne, chief of psychology at Harborview Medical Center in Seattle.
"They have no sense of what another person might go through," he said. "They are what psychoanalysis calls 'malignant narcissists.' They are so preoccupied, they are impervious to considering another individual except as a tool to meet their own needs."
While psychopaths care little for the needs of others, they know social rules exist, said Michelle Rosell, a professor of psychology at Pacific Lutheran University.
"They know what society expects from them, and they just don't care," she said. "They can work well within society's structures. In fact, a lot of times they say people who are antisocial can be quite charming. They can say and do the right things, but they do it for their benefit."
Ridgway knew how to gain his victims' trust. Court documents describe the tactics he used to make them feel comfortable. He flashed his wallet and showed a picture of his young son. When he brought a victim to the house near Sea-Tac Airport where he killed dozens of women, he showed them his son's room, and toys scattered across the floor.
"They look in the bedrooms, nobody's in there," he told investigators. "There's my son's room, hey, this guy has a son, he's not gonna hurt anybody."
In interviews, Ridgway was asked to rate his own evil. Given a scale of 1 to 5, he answered "3," and pointed out that he did not torture his victims.
Once they were dead, the victims became his possessions, Ridgway said - "a beautiful person that was my property."
In his 1997 book, "Signature Killers," Robert Keppel, a consultant on the Green River Task Force and a serial killer expert who once hunted Ted Bundy, describes the behavior of "signature killers" as "a total series of decisions directed exclusively toward self-indulgence."
"The murders themselves are acts representing the absolute of selfishness in its purest, most refined form," Keppel wrote.
Ridgway's self-indulgence sometimes reached the point where he had to resist thoughts of killing family members, he told investigators.
In July 1982, he picked up one victim while his 7-year-old son rode with him in his truck. Ridgway drove to a wooded area and parked. He got out with the woman, left his son inside, told him to wait and walked to an area where the boy could not see.
When he returned after killing the woman, the boy asked where she had gone. Ridgway replied that she decided to walk home.
In 2003, Ridgway told a psychologist he felt "a little bit of remorse" about killing the woman while his son was nearby.
The psychologist asked what would have happened had Ridgway's son seen the slaying. The boy would have been a witness, the psychologist said.
Asked whether he would have killed his son under those circumstances, Ridgway said, "No, probably not, I don't know," though he admitted it was possible.
The psychologist asked whether he thought about it.
"Yeah," Ridgway said.
Ridgway passed a polygraph test in 1984, when investigators tapped him as a potential suspect in the Green River slayings. In retrospect, investigators say Ridgway's psychopathy helped him. The polygraph detects stress; Ridgway had none.
"I just uh, relaxed and took the polygraph," he said.
Roy-Byrne said, "Some people have speculated that psychopaths lack the normal kinds of anxiety and fear reactions that the rest of us have."
"When they're exposed to stimuli that should make them anxious or fearful they don't have the anxiety you'd expect."
Rosell points out that most antisocial personalities don't turn into serial killers. Some can be productive members of society.
"They're just kind of the jerks that you meet," she said. "They may be the people who swindle old people out of money. They leave their families in the lurch. They're not just the normal mean person you meet. They're just a little more extreme. And they do things without remorse."
Keppel sees a "faddish" tendency in the media and the realm of true-crime writing to delve into a killer's childhood and create an "inevitability theory" that explains a murderous career.
That misses a fundamental point, he writes, noting that many of the same pressures faced by those who become serial killers also apply to those who don't.
"It's not just a matter of chemistry or parental abuse or head injuries," he writes. "What it really comes down to is choices."
Staff writer Karen Hucks contributed to this report.
Sean Robinson: 253-597-8486