Thirty-five-year-old Chona Manzano and five-year-old Gabriel Manzano were found dead Thursday in a home on the northwest edge of the city.
Police said a family member was alerted to a problem and went to the home around lunch time.
He found the woman's body on the main floor of the house and the child upstairs.
Investigators soon noticed one of the family's vehicles was missing.
A description of the vehicle was circulated and Mounties located it later in the afternoon about 90 kilometres north of the city, between Didsbury and Olds.
Police Staff Sgt. Doug Andrus said the vehicle was in a ditch and the only person inside was injured. The man was taken to a hospital and treated for his wounds, then released and taken into custody.
News reports show the suspect was escorted to a police car with his wrists and hands wrapped in white bandages.
Guevara Wilson Clorina, 26, faces two counts of second-degree murder. He is to appear in court on Tuesday.
He is related to the dead but is not an immediate family member and did not live in the same home, said Andrus.
He discounted initial reports that extended family lived in the house. He said Chona Manzano lived there with her husband and their three children — Gabriel and two girls.
Her daughters were found safe at another location, Andrus said.
He said her husband is obviously very distraught.
"Of course, he's just lost his wife and child. He is grateful for our investigation and that we've brought it to a conclusion so quickly, but it doesn't replace the loss."
He said counselling has also been offered to police and paramedics.
"This investigation had a significant impact not only on our investigators but the first responders, some who have children of their own."
He said investigators are still trying to determine a motive for the killings, and have several theories.
Police had not been called to the home before and Clorina was not previously known to officers, he said.
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