Damian Clairmont, 22, was from Calgary.
He left for Syria in November 2012 and fought with a group called Jabhat al-Nusra, an al-Qaeda linked group now deemed by Ottawa to be a terrorist organization.
His family told CBC that CSIS had been watching him, but was unable to stop him from leaving the country.
CBC has also learned from sources in Syria and Canada that he was injured in a battle near Aleppo and was eventually believed to be killed by Free Syrian Army forces.
His family has asked for privacy.
More to come