WALLA WALLA - Every serial killer starts somewhere, and for Robert Lee Yates, a taste for murder appeared to have been whetted at a popular swimming hole on Mill Creek, a dozen miles southeast of Walla Walla one summer afternoon in 1975.
There, according to sheriff's investigators and prosecutors, Yates, then 23, came upon a pair of local college students picnicking beneath a stand of poplar trees.
And he shot them both dead.
Even now, nobody is quite sure why.
Sheriff Mike Humphries hopes his investigators will get a chance to ask Yates in detail about the case soon.
The killings here, though, appear to be his first and differ significantly from the prostitute slayings attributed to Yates in Spokane.
"I'd say he was cutting his teeth," said former Walla Walla Prosecuting Attorney Arthur Eggers, now retired and living in Seattle.
Until Yates was arrested in April, Walla Walla authorities had long exhausted their investigation into the slayings of 21-year-old Patrick Oliver, an honor-roll pre-med student who had studied at the Sorbonne in Paris, and Susan Savage, 22, a recent graduate of Washington State University. Oliver is the only man Yates is believed to have killed.
Suspects in the killings had come and gone, according to Larry Siegel, the deputy prosecuting attorney who had the lead in the case.
"We had two or three good suspects, but they ended up going nowhere," he said.
Speculation about what happened along Mill Creek the afternoon of July 13, 1975, had run from the mundane - a robbery gone bad, perhaps - to the extreme.
"At one point, we considered it might have been a professional hit . . . or maybe, somehow, was gang related," Siegel said.
Even Interpol was called because Oliver had recently returned from Europe, but to no avail.
"We frankly ran out of ideas as to why anybody would want to kill them."
There were a few intriguing leads culled from the crime scene. The bodies were dragged, perhaps as far as 30 yards, across the river, and secreted beneath a tire and some brush. Siegel recalled that the woman was partially clothed, or that perhaps both of them were nude. There was no indication, however, that they had been anything but friends.
Siegel said he could not recall any other indication of sexual overtones to the crime. Humphries declined to comment on that aspect of the case.
"But I don't think it was planned," the sheriff said. "I think he ran into them up there and there was some sort of confrontation, and he shot them."
Both victims had gunshot wounds in their arms, indicating they had tried to deflect the shots. Both died from being shot in the head.
"I remember thinking that it almost seemed like an execution," Siegel recalled.
While leads petered out years ago, the sheriff said his detectives made a point to return to the file regularly.
"Every time somebody new would come in they would go through that file looking for something somebody might have missed."
The office preserved all of the crime-scene evidence - slugs from the victims, an old sleeping bag, picnic odds and ends - and all of it is in the evidence room today.
The break came only with Yates' arrest in April. Humphries learned that Yates, who had shot all of his victims in Spokane, was living in Walla Walla and working as a corrections officer at the state prison when Oliver and Savage were slain.
The sheriff opened an investigation and found that Yates had bought a box of .357-caliber shells from a local store 10 days before the killings.
"They matched the caliber and brand of bullets from our crime," the sheriff said. His detectives learned from friends and family that Yates regularly went to the Mill Creek area for target practice.
Yates left the Walla Walla area, where his wife's family lived, shortly after the killings and sold the handgun in Oak Harbor in 1976. Investigators were able to track that handgun through four owners and now have it in evidence.
In exchange for the guilty plea, Yates hopes to avoid the death penalty for the Spokane slayings. Walla Walla County Prosecuting Attorney Jim Nagle said yesterday he has no qualms with that deal.
If Yates were to be tried in Walla Walla, Nagle would have to charge him under murder statutes in effect at the time, when Washington did not have a death penalty.