As unusual as home abductions are, rarer still are kidnappings in which multiple people disappear at one time.

Yet that appears to be the scenario that played out in the case of five-year-old Nathan O'Brien, who vanished along with his grandparents from their Calgary residence June 29.

Calgary police have not designated this an abduction, careful to describe it only as a missing persons investigation. But several details — including signs of a "violent crime," the questioning of an ex-con who allegedly harboured "bad blood" with the missing grandfather over finances, and an estate sale the day before the trio vanished — point to possible foul play.

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)

"Certainly it's unusual for Canada. Logistically, abducting one person, that's hard to fathom, but to get away with taking three people out of a home, if that's what happened here, that would be a lot more difficult," said Janne Holmgren, director of the Centre for Criminology and Justice Research at Calgary's Mount Royal University.

"Especially if it's one person who would be involved in this, that's really quite unusual," she added.

Rare though it may be, a group kidnapping would not be unprecedented in Canada, nor would it even be the first such mystery to take place in Alberta.

Lyle and Marie McCann, 2010

Douglas Garland

Douglas Garland, who was taken in for questioning from a rural Airdrie, Alta., property on Friday, has a criminal history, including drug trafficking and possession of stolen property after he was caught making amphetamines on his parents' acreage in 1992. (Calgary Herald)

Husband and wife Lyle and Marie McCann vanished in July 2010 in St. Albert. The elderly couple were last seen filling up their vacation motorhome, and their RV was found burning two days later near a campground.

Their bodies were never found. Travis Vader, 42, was charged with two counts of first-degree murder. The charges were later stayed.

Johnson sisters and family, 1982

Mass murderer David Ennis killed six members of the Johnson and Bentley families in 1982 at B.C.'s Wells Gray Provincial Park, kidnapping the Johnson's daughters for six days. They were sexually assaulted before they were killed.

Ariel Castro hostages, rescued 2013


Lyle and Marie McCann were last seen on July 3, 2010. (CBC)

Ariel Castro's kidnappings of one young woman and two teen girls was perhaps the most notable recent example of multiple people being snatched in the U.S. However, the three victims vanished on different dates. Police eventually rescued Amanda Berry, Gina Dejesus and Michelle Knight in 2013. Knight, the longest survivor, had at that point spent 11 years as a prisoner in Castro's basement in Cleveland.

Jaycee Dugard, rescued 2009

Michelle Knight

Michelle Knight is one of three woman held captive for years by Ariel Castro in his Cleveland home. (Tony Dejak/Associated Press)

Jaycee Dugard was held captive for 18 years after she was abducted in 1991 at the age of 11 in South Lake Tahoe, Calif. Police rescued her in 2009 and her captors, convicted rapist Phillip Garrido and his wife Nancy Garrido, were arrested and sentenced to 431 years and 36 years to life, respectively.

Most missing children found quickly

With so much time expiring, retired FBI agent Kenneth Lanning said it's easy to panic over research on missing children and survival rates. Lanning, a 30-year veteran of the FBI who spent 14 years consulting agents on crimes against children, said that in 70 per cent of missing child homicide cases, a child is murdered within three hours of the abduction.

But he cautioned that those kinds of statistics can skew public perceptions of how endangered a missing child's life is.

"What people don't understand is that most abducted children aren't murdered," Lanning said. "Most of the time, 99 per cent of abducted children are released."

Multiple victims: relationships matter

Little is known about the Calgary disappearances, but Lanning said it's likely Calgary police know a lot more than they are letting on.

He noted that child abductions are often linked with some presumption of a sexual motivation on the part of the perpetrator. When Lanning started in the 1970s, he said, the presumption was that a kidnapping was tied to a ransom demand.

'According to the Calgary police, we're still hopeful we'll find these three individuals alive, and the positive thing is there's still information coming in.' - Janne Holmgren, Mount Royal University criminology professor

"But what's important here is in most missing children's cases, you don't usually have multiple victims," he said.

"The reasons you might abduct a grandmother or grandfather are different than the reasons you might abduct a boy. Is this a burglary gone bad? A break-in gone bad? Did the granddad double-cross somebody in a business deal? Is this some pervert who wanted the kid, but grandma and grandfather were there? These are all things investigators have to consider."

It's easy to get lost in the details of the case, said Neil Boyd, director of the School of Criminology at Simon Fraser University. The problem is so much is uncertain to the public about what happened in that Calgary home and why.

"We have a cast of characters, we appear to be able to connect the dots to something, but we're not able to impose any meaning to be able to say with any certainty what's likely to have happened," Boyd said.

"The fact that it's two grandparents and a grandchild, it doesn't alter the dynamics [of the investigation] that much."

Holmgren seemed to think otherwise.

"This is a very different investigation than if it was solely a child abduction," she said, adding that she often reminds her criminology students at Mount Royal that relationships matter a lot in abduction cases, and that such cases involving strangers are very uncommon.


Jaycee Dugard was held captive for 18 years after she was abducted in 1991 at the age of 11 in South Lake Tahoe, Calif. (People/Associated Press)

The person of interest questioned in the Nathan O'Brien case, Douglas Garland, has a connection to the Liknes family through his sister.

"It's clear to me our investigators know a lot more as to what's going on than they can give the public," she said. "According to the Calgary police, we're still hopeful we'll find these three individuals alive, and the positive thing is there's still information coming in."

Anyone with information about the case can call the Calgary Police Service at 403-266-1234 or Crime Stoppers anonymously at 1-800-222-8477.