A Calgary man accused of killing his two children is now facing charges of first-degree murder. James Bing Jun Louie was originally charged with second-degree murder but the charges were upgraded Monday.

Louie, 43, now faces two counts of first-degree murder and one count of attempted murder. He made his first court appearance via closed-circuit television Monday.

Louie was arrested after police entered a Calgary home Friday night and found the bodies of a 13-year-old boy and a nine-year-old girl.

Police said it appears a woman, reported to be the children's mother, was the first to come across on the scene.

"The preliminary information indicates that she had arrived home and that's where the first contact was made with the police," Insp. Guy Slater of the Calgary Police Major Crimes Unit said at a Saturday news conference.

Calgary Police told media over the weekend that after officers discovered the children's bodies, they continued searching the home and found a man and a woman involved in a struggle upstairs.

Police Chief Rick Hanson said they believe the officers' intervention may have interrupted a "potential homicide".

The woman was taken to hospital where she was treated for minor injuries.

A Facebook memorial page has been set up to honour the memories of Jason and Jane Louie. The Calgary Board of Education said crisis counsellors will be made available for staff and students at the schools attended by the slain children.

Louie's lawyer, Noel O'Brien, had the case put forward to Dec. 14 so he can receive more details about the case.

With files from CTV Calgary and the Canadian Press