Of the head-scratching details surrounding the disappearance of five-year-old Nathan O’Brien and his grandparents, an estate sale held the day before the trio vanished from the Calgary house is possibly among the most compelling.

As many as 300 strangers likely wandered through the residence of Kathy and Alvin Liknes, as part of the estate sale throughout last weekend. Nathan, their grandson, slept over.

Kathryn Liknes, Nathan O'Brien and Alvin Liknes

Nathan O'Brien, centre, and his grandparents, Kathy and Alvin Liknes, have not been seen since Nathan's mom left the home of the couple the night of June 29. (Calgary Police Service)

Now police want to interview all prospective buyers who visited the property.

No connection has yet been established between what appears to be a violent crime and the three-day event advertised online through the Kijiji classified network.

But the missing persons case could serve as a reminder of the dangers associated with online transactions and estate sales, especially as technology becomes more ubiquitous, said retired homicide detective James Jewell.

“These online venues didn’t exist 20 years ago, and so it’s becoming more prevalent that people are exposing themselves to danger,” the 26-year veteran of the Winnipeg Police Service said. “It’s obviously very disconcerting when people invite people into their homes, or have estate sales, or meet people through chatrooms online, or even internet dating.”

Reminiscent of Tim Bosma case

Violent home invasions following incidents in which perpetrators cased a residence have not been historically common in Canada, Jewell said. But he predicts “it's going to happen more and more as technology continues to evolve and people start using these websites more to meet people not known to them.”

mb-irene-pearson

Real estate saleswoman Irene Pearson, 31, was found dead in a vacant home in the Tyndall Park area of Winnipeg on Nov. 16, 1979. ((Winnipeg Police))

The use of the classified website Kijiji is reminiscent of the case of Tim Bosma, an Ontario father who was slain last year after arranging to go on a test drive with two men who expressed interest in buying his truck. He had also posted an online ad to the classified service.

Following the reports of Bosma’s disappearance, Kijiji released a statement reminding users to beware of fraud and to meet in-person with interested buyers or sellers at crowded public places such as coffee shops.

In an email to CBC News, Kijiji's community relations manager, Shawn McIntyre, wrote that the Bosma incident in most likelihood "did not occur as a result of his ad posting," as it was later determined that his ad "did not feature personal contact information, nor did he receive any replies."

User safety is "paramount," McIntryre added, and said the website works with law enforcement agencies to ensure that's the case.

Jewell worked more than 200 homicides during his years with the force. A vast majority of cold cases “come back to people being exposed to strangers,” he said.

Consumers who want to protect themselves when buying or selling items with strangers must be wary of “inviting strangers into their world,” he said, advising people to do their transactions in a neutral or public area instead.

B.C. real estate agent Lindsay Buziak was showing a million-dollar home to a couple in Greater Victoria by herself, police said, when she was stabbed to death in an upstairs bedroom six years ago.

Lindsay Buziak - Victoria realtor killed in 2008

Lindsay Buziak, who worked as a realtor, was stabbed to death while showing a home in Greater Victoria, B.C., on Feb. 2, 2008. (CBC)

Long before Jewell became a detective, he recalled his father discussing the still-unsolved 1979 murder of Irene Pearson, a real estate salesperson for Castlewood Homes. The woman’s body was found in the basement of a vacant home in northwest Winnipeg.

“My dad was a building inspector for Castlewood Homes at the time,” he said. “That’s a case that really jumps out at me.”

Private investigator Dave Perry has worked on many child abduction probes, including the high-profile cases of Holly Jones and Cecilia Zhang, during his 28 years with the Toronto police. Although he has never encountered a kidnapping in which an estate or property sale advertised online was a motive, Perry said would-be thieves are increasingly gleaning information posted online by people detailing their vacation plans, or even combing through obituaries.

“It’s very common,” he said. “Families have a loved one who is just deceased, people are away and grieving, busy with the funeral, so people’s houses are broken into.”

Craigslist entrepreneur's advice

It’s often wiser for anyone interested in advertising estate sales to have a third party set it up, too, he added.

“Use some of the profit to have a third party do it for you and keep you distant.”

Ryan Finlay, who makes his living buying and selling mostly electronic appliances over the online classified website Craigslist, estimates he has dropped in on dozens of estate sales in the past four years.

The Portland, Ore.-based entrepreneur offered a few safety considerations to people planning estate sales:

  1. Hold an estate sale after you have already moved out of the house. “Because if you’re going to indiscriminately invite the public to your home like that, they can learn a lot of information about you,” Finlay said. “An elderly couple’s home might have have medical equipment, wheelchair lifts, things that could reveal disabilities or other vulnerabilities [criminals] could later attempt to exploit.”
  2. Communicate via prominent signage or in the ad that no money will be left at the home after the sale. “If a criminal realizes there’s a pile of cash sitting at the house, it might tempt that person to come back.”
  3. Try not to hold an estate sale in a rural area that’s too quiet.
  4. Don’t buy or sell in a parking lot. Although Finlay said parking lots may seem safe because they are open, public spaces, “thieves want to control their environment” and have been known in the past to “set up” conditions to pull off robberies.
  5. As a preventative measure, avoid having an estate sale in the first place and gradually shed property over time.

Finlay added that it’s important to keep some perspective, noting that he has completed some 6,000 Craigslist transactions without ever feeling like he was in danger.

Perry, the Toronto private investigator, stressed it’s important not to blame the victims in the Calgary case.

“Nobody in that scenario did something wrong,” he said.

These types of crimes are still rare enough that he’s cautious about pushing any kind of reactionary response.

“I’m not here to say people should stop using Kijiji or never have an estate sale but you need to practise some safety and common sense when you’re doing this kind of stuff,” Perry said.

“I still have the belief that when a crime is committed in Canada, it doesn’t mean we all of a sudden change our behaviour.”