Edmonton police are investigating the explosion and fire Tuesday at the Bethany Senior Citizen Home in Old Strathcona as a homicide.
Two people died in the fire.
While police are investigating one death as a homicide, they are not looking for suspects.
One victim has been identified as Bethany resident Anna Fedorio. Sources tell CBC News the other victim was a man who also lived in the southside seniors complex.
Police believe the fire and a separate car fire in the parking lot of the complex were deliberately set.
"It was around 12:30 when we heard this 'Boom,'" said Kari Heise, who lives next to the six-storey building at 99th Street and 83rd Avenue.
"We saw a car completely engulfed in flames behind the seniors building beside us."
After calling 911, Heise and her husband ran outside and saw the seniors complex on fire as well.
Firefighters had the fire under control by 2:10 a.m.
Arson and homicide detectives will spend the next couple of days searching through the debris, said Det. Dwayne Lakusta.
About half of the 59 seniors are now staying at a southside hotel.
Resident Matthew Renn saw the car on fire before an explosion rocked his suite.
"The one wall inside was just opened like a door, my furniture is upside down, my bed was (moved) two feet," he said outside the Ramada Inn on Calgary Trail. "I fell down. I smashed my big finger."
Firefighters had to rescue him from window, because the hallway was too hot, he said.