The Calgary Fire Department broke windows to vent the home of carbon monoxide gas. (Meghan Grant/CBC)

The carbon monoxide deaths of a mother and her six-year-old son have been confirmed as a murder-suicide, say police.

Calgary police Duty Insp. Paul Stacey said Chia Ming Liu, the boy's father, called 911 Thursday night after arriving home to find his wife, Yu-Mei Lai, and his son, Kevin Liu, dead.

"The father is very distraught. We called out our victim support team to help the father and other family members," Stacey said.

When police arrived at the Varsity home in northwest Calgary just after 9:30 p.m. MT Thursday they found indicators of high levels of carbon monoxide.

Police say they found a suicide note and located both the mother and son in a bedroom.

“The manner of death for the female has been deemed suicide, while the manner of death for the boy has been determined to be homicide,” said police in a Friday afternoon news release.

Next door neighbour Sarah Kowatch said the family was of Asian descent, were quiet and kept to themselves.

“I remember seeing them carrying the little boy out but at that point we didn't know what happened and I remember thinking, 'Oh my gosh, I hope he's OK,'" Kowatch said.

"We never really saw much of the dad, but the mom and the little boy we would pass them going to our cars or coming in and out of our houses. They seemed very nice.”

The family had been in Canada for more than a decade.

Common family violence causes

Christine Berry, a psychologist at the Calgary Counselling Centre, said many situations of family violence stem from situations dealing with mental health.

“They are very distressed. They're in a lot of emotional pain and sometimes their thinking is ‘I am in this kind of pain, that's not okay. So, I'm going to save my child from this kind of pain’ and they then murder the child,” said Berry.

Revenge can be another motivator, said Berry, pointing to cases where parents kill children while in a custody battle.

She also said that the stress of immigration can sometime be a factor.

“The whole process of assimilating to a new country, new rules, new beliefs, new ways of acting that's pretty overwhelming and challenging for anybody,” said Berry.

“If that's in the environment, and there's all kinds of isolation, a sense of things aren't getting better — so, there's no sense of future. And again, we're just speculating, there could be so much pain in that individual that they think it's better idea to remove the child from that kind of a painful life."

Kevin Liu’s death is Calgary’s 13th homicide of 2012.