The crimes are less than five months old. The violent sex offender who committed them has likely been active for far longer, according to an FBI profiler.

Air Force colonel Russ Williams stands charged with two first-degree murders and two sex assaults in and around CFB Trenton. He is 46.

On Tuesday morning, police were poring over unsolved crimes in the many stops in Williams’ 23-year military career, including towns small and large across Canada, as well as overseas postings.

Williams stands accused of an escalating rampage of violence. First, a pair break-and-enters followed by fetishistic sex assaults over a two-week span in September. Both targeted homes were on the same road. Both victims’ identities are now shielded by court order.

Then, on Nov. 25, Cpl. Marie-France Comeau, 37, was found slain in her home in nearby Brighton. On Jan. 29, 27-year-old Jessica Lloyd disappeared. Her body was recovered Monday, the day after Williams was arrested.

Police are not revealing the details surrounding the murders. They have said that in both sexual assaults, the victims were surprised in their homes late at night. They were tied to chairs. They were photographed by their assailant. A report in the Toronto Sun provided details of one attack, which included an unhurried intruder who seemed calm throughout.

We asked Mark Safarik, one of the FBI’s serial-killer hunters with the famed Behavioral Analysis Unit, about the likelihood that crimes like that were the work of a first-time offender.

After 22 years in the bureau, Safarik now operates a Virginia-based consultancy with Robert K. Ressler, the FBI investigator credited with popularizing the term “serial killer.”

After considering some of the published details, Safarik observes, “People don’t just wake up one day and say, ‘I’m going to abduct someone and murder them.’ I’m sure there’s a history.

“For me, the surprise is the number of assaults in a relatively short period of time,” Safarik says. “He’s obviously intelligent. He’s careful. So what’s happening with him? Is there some sort of mental decompensation? Did something trigger this?”

According to the profile of this sort of violent sex offender, “Usually there’s a progression,” Safarik says. “First, prowling, peeping, non-violent paraphilic (sexually deviant) stuff, voyeuristic activities. At some point, offenders decide that’s not enough. They’ll cross that line into fantasy fulfillment. He may have acted out with willing partners initially, prostitutes or others. And then that isn’t enough of a thrill, and he crosses over into non-compliant victims.”

The offender in the latest crimes sounds like someone at the mature end of that progression, Safarik believes.

“He’s comfortable in the environment. He’s breaking in. He’s staying for long periods of time. He’s engaged in other activities – binding, photographing. That isn’t typically behaviour that just starts.”

Safarik suggested that, aside from other violent sex crimes, police will be looking for reports of unsolved “precursor” crimes in places where Williams has lived.

“I would be looking for cases where we tend to see sexual components that aren’t necessarily seen as sex crimes,” he says. “For instance, night-time burglaries where someone’s house is broken into but nothing is stolen. Or fetish-type burglaries, where they’re taking clothing.”

The search will be complicated by several factors, Safarik says. First, there’s Williams’ job.

“He’s in the military. That’s a problem. Not only has he moved around, the people around him have moved around.”

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There’s also a massive time gap to fill in.

“I’d be checking back into his late teens. I’d probably start at age 18,” Safarik says. That would leave police poring over cold case files, many of them seemingly minor crimes, going back to early ’70s.

“I’d be running the whole gamut, going deep into this guy’s history,” says Safarik. “I know that’s what they are doing.”