In an email to The Canadian Press, Teena Prevost, a sister-in-law of Kathryn Liknes, said her family is praying police are wrong.
"Until the police can show us the bodies of our loved ones we will not believe they are deceased," she wrote. "Praying we will find them alive."
Teena is married to Randy Prevost, the brother of Kathryn Liknes, and wants people to know that family is suffering as well.
"Her siblings seem to be all forgotten in all this mess," she said. "Kathy was an amazing sister and sister-in-law."
Calgary police Chief Rick Hanson told reporters a man was arrested early Monday, but couldn't be identified until he appeared before a justice of the peace on the charges later in the day or early Tuesday.
The man is to face two counts of first-degree murder in the deaths of Alvin and Kathryn Liknes. One charge of second-degree murder is to be laid in the death of five-year-old Nathan O'Brien.
Hanson said the man in custody is from Airdrie, a community north of Calgary, but would not confirm media reports that it is Douglas Garland. The 54-year-old lives on an Airdrie acreage with his parents and was earlier questioned as a person of interest in the case.
Hanson would only say police are not looking for any other suspects.
The missing family members were last seen two weeks ago, on June 29. The couple held an estate sale at their home that weekend and their grandson stayed for a sleepover.
When his mother went to pick him up the next day, no one was home.
Police have said there was evidence something violent had happened in the grandparents' house, but always believed there was a chance they could be found alive.
Shortly after the three disappeared, Nathan's parents issued a tearful plea through the media asking for their return and urging their "superhero" son to be brave.
"Even as the days went by there's always a hope, there's always a glimmer of hope," Hanson said. "Unfortunately with the laying of the charges, we've taken that hope away from the family. So they are devastated."
After news of the arrest, flowers starting piling up in front of the grandparents' home. A note next to some candles read, "I believe."
"I hope they're wrong and they will find them," said neighbour Natalie Stevenson. "To think of losing my parents like that or my son would just be a nightmare."
While refusing to discuss the evidence in any detail, Hanson said there is no "smoking gun" that finally led to the arrest and the belief the three are dead.
Investigators met with Crown prosecutors on Sunday to go over evidence that had been gathered over the two weeks, he said. They determined charges were warranted. An Amber Alert issued shortly after the family members were reported missing was also cancelled.
"It was clear at that point that this was no longer a missing persons investigation. This was a homicide investigation," Hanson said.
From the beginning, the case captivated people across the country. Thousands of people wrote messages on a blog for the family and police received more than 900 tips from the public, including sightings reported from coast to coast.
Despite the charges, the police chief said the case is not closed and investigators will continue to search for bodies of little Nathan and his grandparents.
Hanson renewed calls for rural property owners to search their land for anything out of the ordinary.
Garland was first questioned more than a week ago, then held on unrelated identity theft charges. He was released from custody on Friday. His lawyer on those charges, Kim Ross, did not return messages seeking comment Monday.
Investigators have been searching his parents' acreage northeast of Airdrie, including several fields and sloughs on and around the property.
Garland has ties to the Liknes family. His sister is in a relationship with a member of the Liknes family.
Police earlier said they were looking into whether there was a business connection to the missing persons file.
Alvin Liknes was involved in several oil and gas companies, including Winter Petroleum Ltd., which media reports say was forced to close a few weeks ago. The CBC has quoted a police source as saying Garland and Alvin Liknes had a dispute over a patent for a gas device.
Court documents show Garland has a criminal record and mental issues.
In 2000, he was sentenced to 39 months for making amphetamines at his parents' farm. Before he went to prison, he jumped bail and lived for several years in Vancouver using the identity of a dead person.
The Parole Board of Canada gave him accelerated release after six months, noting in its decision that Garland's prior criminal record consisted of various property offences over the course of 20 years.
His mental health played a role in the crimes, the board said, but a psychologist determined that Garland had "little violence potential to others.'' It ordered a psychologist and psychiatrist to closely monitor him during his release.
Prime Minister Stephen Harper sent out a message of condolence on Twitter Monday.
"Our thoughts and prayers are with the O'Brien and Liknes families during this time."
Alberta Premier Dave Hancock and Calgary Mayor Naheed Nenshi also offered their condolences.
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