Jessica Lloyd was strangled by her killer, according to a source who says the death of the 27-year-old from Belleville was the ultimate crime in a "bizarre escalation" of behaviour.
A second alleged victim of Canadian Forces Air Force Colonel Russell Williams was also asphyxiated, sources familiar with the investigation say. But detectives believe the death of Canadian Forces Corporal Marie-France Comeau, 38, was not intentionally inflicted. "The theory is that she was meant to live."
Col. Williams stands accused of first-degree murder in both cases. He is also charged with two counts of sexual assault stemming from attacks on two women who live close to his Tweed-area cottage.
As well, he is under scrutiny in less severe crimes - starting with the thefts of women's underwear dating back to 2006.
A source said police are probing 48 such cases and have recovered stolen lingerie - neatly stored, catalogued and concealed - in searches of the suspect's Ottawa home.
The investigative theory is that Col. Williams graduated from the years of panty raids to sexual assaults, and then to murder.
In July, he took command of 8 Wing/Canadian Forces Base Trenton, Canada's largest Air Force base. In September, two women were bound with tape and blindfolded by a man they could not identify.
Those attacks took place two months before Col. Williams's subordinate, Cpl. Comeau, was found slain in her home. A source said she had been gagged and blindfolded before the killing.
Ms. Lloyd, who worked for a school-bus company, disappeared on Jan. 29. She had just sent a text message to a friend saying she was safely inside her home in Belleville, a community east of CFB Trenton.
Police were led to her body in the woods near a rural roadway in Tweed, northeast of the army base, after Col Williams's arrest and interrogation this past weekend.
Ms. Lloyd's funeral is to take place this weekend. Col. Williams is being held in the Quinte Detention Centre in Napanee.
The "bizarre escalation" theory casts doubt on growing public speculation that the alleged pattern of sex crimes could incorporate decades-old "cold" cases of homicide or sexual assault.
Detectives probing the Eastern Ontario murders have been flooded with calls from Manitoba and Nova Scotia as concerned citizens and police ask whether the ongoing investigation might shed light on old crimes.
During the 1980s, Col. Williams attended high school and university in Toronto. He joined the military and was posted to bases in Western, Eastern, and Central Canada in the 1990s.
Before his arrest he had an unblemished career.
The Ontario Provincial Police say their priority remains gathering evidence on the current cases, and they're not dusting off legacy files just yet.
"Right now, the core investigation is still around the four incidents now before the courts," said OPP Sergeant Kristine Rae.
Police are still scouring those crime scenes, she said. Sgt. Rae acknowledged that police and families of other missing women have been calling.
The OPP will not say whether they have obtained a DNA sample from Col. Williams - although it is likely, given the ongoing searches of his properties.
His genetic code will likely prove an invaluable tool in the investigations, regardless of whether it implicates him in other crimes or clears him of suspicion.
Parliament passed laws creating a national DNA databank in 2000, allowing police look for matches with evidence obtained from crime scenes.
Police can re-examine old crime-scene evidence, such as hair, blood and semen of potential suspects, because biological material can survive for years after a crime takes place.
Samples are sent to forensic scientists who input the code into the "crime scene index," or CSI component, of the national DNA databank, which is run by the RCMP.
The oldest scrap of evidence in the national databank is from 1964 - decades before the forensic science based on genetic code became a reality. The database has DNA evidence from more than 50,000 crime scenes.
"I like to look at the DNA databank as a justice time machine," Ron Fourney, the scientist in charge of the databank, said in an interview. "DNA is often a silent witness."
He said he could not comment on individual cases.
Meanwhile, police are said to be investigating whether there are any ties between Col. Williams and serial killer Paul Bernardo, according to a report Friday in the Toronto Sun which said the two were "pals" during their university years. Police sources have said there is currently no known connection between the two men.
Col. Williams and Mr. Bernardo attended the University of Toronto's Scarborough campus at the same time, Col. Williams graduated in 1986 and Mr. Bernardo in 1987. Col. Williams studied economics and political science while Mr. Bernardo obtained a BA in business.
Mr. Bernardo, who was later convicted of killing three schoolgirls in the early 1990s, has admitted to raping at least a dozen women in Scarborough at that time.
With reports from Colin Freeze and Greg McArthur