He is accused of killing his father, Luc Gélinas, 54, and his father’s partner, 35-year-old Julie Lemieux.
The two were found dead in their Terrebonne, Que., home on Thursday morning. Radio-Canada reported the couple had been stabbed with a sharp object.
Guillaume Gélinas was arrested in Gatineau on Friday after police traced his cellphone. He is listed as living in Gatineau on his Facebook profile.
Gélinas was in the Canadian Armed Forces reserves and spent some time in Afghanistan between 2010 and 2011.
Luc Gélinas wrote on his Facebook page on July 20, 2011, that his son had finally returned after more than eight months in Afghanistan. The above photo of the couple with Guillaume was uploaded to Facebook the same day.
Some people who knew Guillaume Gélinas said he had recently been going through a hard time, although little is known about the condition of his mental health.