I have found an Etienne Gagne living in Ste. Marguerite, Dorchester, Quebec in the 1911 census. If this is him, he was born October 1881, his wife Albertine was born December 1884, and they had two children at the time: Joseph (born April 1910) and Maria (born March 1911). They are living next to another Gagne family (possibly a brother?), family head named Augusta.
Etienne and his wife returned to Quebec in 1942, settling at St. Paul Ermite. They had came west around 1912.