Disbelief and mystery settled on a quiet, upscale Calgary neighbourhood Wednesday after word that a one-year-old girl was the only survivor of an apparent “domestic homicide” that left three adults and two young children dead.

“She's doing very well,” said Calgary police Insp. Frank Reuser, who was badly shaken by what he'd seen at the house. “She's doing a lot better than me.”

An officer gently carried the small child in a blanket-draped baby-carrier to a waiting car as horrified neighbours looked on behind police tape that roped off the entire street.

Hours later, after police attained a warrant and began investigating the grisly crime scene, chief Rick Hanson suggested the killings were part of a murder-suicide involving an entire family and another adult.

The dead included two little girls, aged four and six, as well as both of the girls' parents and a third adult female who police believe was a tenant.

Chief Hanson said a family member initially called police around 10 a.m. Wednesday after they went over to the house and “saw something that wasn't quite right.”

The scene was so disturbing that the five officers who made the discovery and the emergency medical services crew were given trauma counselling.

“Any time there's a crime that involves children it has huge organizational trauma associated with it,” said Chief Hanson. “Personally, I can't recall an incident that's involved this many people.”

Police said initial records show they had never been called to the house for any previous domestic incidents.

Calgary's homicide unit had to wait until late afternoon for a search warrant to re-enter the house and begin their investigation.

Police were tight-lipped over the cause of death and other details of the crime scene, including how long the infant was alone in the house.

And Chief Hanson said his officers will take all the time they need to try and figure out what happened.

“When you have a crime scene that's this horrendous; when it's this traumatic; when there's a family involved, there's so many unanswered questions.”

Grim-faced residents stood on their lawns and watched as an array of police vehicles, media trucks and a circling helicopter overhead turned their tree-lined northwest Calgary neighbourhood into front-page news.

“This is a perfect place to grow up – peaceful,” said Graham Hiebert, 20. “We've never had anything like this happen.

“At this point I'm hoping they're dealing with the elementary school, that there's counsellors over there. That's, I guess, all you can do at this point.”

Paul Lapointe, a spokesman for Calgary Emergency Medical Services, said when paramedics arrived at the house, one of them immediately took care of the baby girl while others checked the five bodies.

“Our paramedics are trained to deal with tragedies,” he said, but quickly added that the young children involved made the scene particularly bad.

“Initially our focus was on the baby ... and thankfully the baby was fine. Now our focus is turning to the emergency crews that were on scene.”

Neighbour Mia Albino said the situation was surreal.

“They're just down the street. I just saw them last week,” she said.

“My little guy was going to be going to the same school as his little girl, and we've had lots of conversations on our street.”

Ms. Albino described the family who lived at the house as “great people – everything seemed to be normal.” She said they were church-going, active in the community and always around.

She said her normal morning routine getting ready for work ground to a halt as police cars raced down the street.

Investigators were quick to canvass the neighbourhood looking for clues, but Ms. Albino said there wasn't much she could offer.

“They weren't a family that did anything crazy there were no disturbances – and they were very loving. Every time I saw them they always had their kids with them, hugging and kissing.

“It really does blow my heart apart. I can't imagine doing that to my kids, let alone thinking about it. Something must have really been wrong.

“I don't understand and I'm at a loss for words as to why something like this would happen to that family.”