CALGARY -- A resident at a southwest Calgary seniors' facility has been charged in a fire that sent a fellow resident to hospital with life-threatening injuries.

Firefighters were called to Wentworth Manor 5700 block 14th Avenue S.W. shortly before 1:30 a.m. Monday for reports of a fire.

Mike Conroy, president and CEO of The Brenda Strafford Foundation, which owns and operates the facility, says staff were alerted to the fire by an alarm but the considerable amount of smoke prevented them from entering the room. The resident was evacuated from the room by Calgary Fire Department members.

"We know this will come as difficult news for our residents, families, staff and community at an already challenging time," said Conroy in a statement. "The Brenda Strafford Foundation and Wentworth Manor remains focused on providing the best possible care and services to all of our residents and families."

More than 200 people reside at the three-storey retirement and supportive living dementia care facility.

The man who set the fire was a resident in his 70s who suffers from a mental health condition, Calgary police say. He has been charged with one count of arson.

The condition of the resident who was taken to hospital — a man in his 80s — is still listed as life-threatening.

"This is an extremely sad case," said Staff Sgt. Martin Schiavetta. "We believe that the offender was suffering from a significant cognitive impairment at the time of the incident and we are continuing to support all of the families involved."