Police believe a father and his grown daughter, whose bodies were found in the rubble of burnt-out home near Castor, Alta., were murdered.
In December, the remains of 61-year-old Gordon Klaus and his daughter Monica Klaus, 40, were found in the family home, east of Red Deer.
Sandra Klaus, 62, has not been accounted for, but police believe she too has been murdered.
Sgt. Josee Valiquette said it's possible the woman's body could have been destroyed in the intense fire.
RCMP, who had previously said they considered the deaths suspicious, now say the fire at the Klaus family home was deliberately set.
The family's dog was found shot to death.
RCMP do not believe the killings were random.
"We believe that this was unique to this family," Valiquette said.
Police believe a 2003 white GMC Sierra truck, associated to the Klaus farm and found abandoned 27 kilometres north of the home was used by the killer or killers to escape from the property.
The Klaus's son, Jason Klaus, 38, who lives across the field from the family farm, expressed concerns in an interview with CBC News in December that he was being treated by RCMP as a suspect.
"I'm frustrated. I'm pissed off. I'm everything," he said.
"They think they can feel what I'm going through. No. Nobody can. I don't care who it is. We lived together. We farmed together everyday. We did everything together. That was my life over there."
Klaus said he received a phone call and went over to find his parents' house on fire.