The post on Randy Janzen's Facebook page says that he killed his daughter to relieve her of migraines and depression that had been plaguing her since elementary school.
He then killed his wife, Laurel, the post says, because, "a mother should never have [to] hear the news her baby has died," and his sister, Shelly, "because I did not want her to have to live with this shame."
The CBC cannot confirm that Randy Janzen actually wrote the post. He has not responded to attempts to reach him today.
The post emerged following overnight news of a house fire on Llanberis Way, east of Chilliwack, that turned into a police siege and homicide investigation.
CBC News has discovered that an R and L Janzen are listed as living at 10003 Llanberis Way, the residence where the fire took place.
The Chilliwack School of Performing Arts posted a message to its Facebook page Friday morning, remembering former student Emily Janzen.
"Today we celebrate the incomparable Emily Janzen," the post says. "A former student and instructor, forever a part of our CSOPA family. We will fondly remember her bright smile, beautiful voice and amazing spirit. She will be greatly missed. Our condolences go out to all her family and friends."
Police have yet to confirm any details of what took place at the address on Llanberis Way.