All I found was the death registration.
Rebecca Jackson, died 21 June 1876, female, 23, married, b Lucan Ont, cause of death: gunshot wound/shot dead, informant: Joseph S Cole clergyman Church of England Bracebridge Ont, registration # 009154. Macauley Tsp Muskoka.
Buried Stoneleigh Anglican Cemetery Bracebridge Ont.
Here is a site for all hangings in Canada but I don't see Rebecca on the victim list.
http://www.capitalpunishmentuk.org/canada.htmlTry the Huntsville Library. They have the Huntsville Forester microfilm copies but looks like they don't go as far back as 1876.