The Calgary man killed by police following an armed standoff in Huntington Hills Sunday was 53-year-old David McQueen, CBC News has confirmed.

His longtime caregiver, Isabelle Templeton, talked to McQueen on the phone yesterday as police surrounded the house. She went to the scene and tried to talk to him, but was barred by police.

"We heard the shots fired. We heard when we were sitting out on the street talking to the police officer," Templeton said.

"We didn't know what was happening, but we knew something was going on."

She said McQueen used to call her his "Calgary mom" and that she's not sure exactly what pushed a "very gentle and very caring man" over the edge.

"Nothing like this ever came up. I just don't know what triggered it," Templeton said.

"Something did, but I think a lot of it was pain. Just pain. He was in so much pain."

'He just got kind of desperate'

She said McQueen was frustrated with the healthcare system and the government and was stuck in a broken wheelchair with no proper homecare. She also said he was angry and distrustful of police.

"I think he just got kind of desperate. I don't know. I know I was getting desperate, just going to see him, and there was nothing you could do."

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McQueen's Facebook page contains numerous, lengthy posts complaining about his perceived mistreatment at the hands of the federal and provincial governments, and the healthcare system.

He describes how he suffered a spinal injury after diving into Calgary's Sikome Lake in 1994, not realizing how shallow the man-made body of water actually is, and subsequent, unsuccessful attempts to sue the Alberta government over his injury.

McQueen was a quadriplegic who still had some use of his arms, according to a neighbour who spoke on condition of anonymity.

Mental health

Several of McQueen's publicly available Facebook postings relate to fears that his computer and phone were being monitored by authorities, and of his belief that his politically "connected" neighbours were conspiring against him.

Alberta Liberal leader David Swann released a statement saying McQueen had "reached out frequently" to his constituency office and that his story was one of many in Alberta of people falling through the cracks.

"He was suffering from an obvious, and serious, mental illness and it was often difficult to understand where he was coming from or how we could help," wrote Swann.

"David was also angry. Angry with the injury which all but paralyzed him, angry with a system he felt failed him, and angry with those who represented that system."

Swann says this is just another example, albeit a violent one, of how the system needs to change.

Isabelle Templeton was David McQueen's longtime caregiver. She says he was frustrated with the government and the healthcare system. (CBC)

Grief, anger over dog's death

Many of his posts include photos of his dog, including one on Jan. 15 indicating his beloved pet had died.

That post veers from expressing grief about his loss to anger at Calgary police and a Calgary politician, as well as his neighbours.

"After he lost the dog, he was just lonely because there was no one to talk to," said Templeton, who also said the reason healthcare workers wouldn't visit McQueen was because of the dog.

McQueen also posted an image online of an Easter Seals video in which he appears, along with his dog.

Stephanie Rosch, a spokeswoman with Easter Seals in Calgary, said she knew of McQueen and confirmed the video was filmed as part of a public-service announcement in 2009.

"We are very saddened to hear the news of the passing of Dave McQueen," Easter Seals Alberta Susan Boivin CEO said in a statement. "He was a former client of Easter Seals' Equipment and Support Services program, but we have not had any contact with him for many years."

McQueen indicated on Facebook that he had been visited by police in the past and was angry at how they had treated him.

'Extremely dynamic' situation

Calgary police Chief Roger Chaffin said Monday the shooter was previously known to officers but had no affiliation with organized crime.

More than a dozen officers responded to the "extremely dynamic" situation in the northwest community at about 4:40 p.m. MT Sunday, Chaffin said, on reports of a gunman firing from a home, apparently at anything and everything.

The first 911 call came from a bus driver who was narrowly missed by a bullet that travelled through the transit vehicle's windshield, according to police.

The situation escalated when the suspect exited the home following an hours-long standoff and police responded with gunfire of their own.

McQueen had no criminal record in Alberta, according to a search of court documents.

The Alberta Serious Incident Response Team (ASIRT) is investigating

Chaffin said he expects the shooter's motivation to be addressed as part of the investigation.

The chief also stood by the actions of the officers responding to the incident.

"We were very concerned about the well being of our officers and the public in this case," he said.