Now he's adjusting to a new life in his aunt's home.
Family friend Tracy Rhodes told CBC Daybreak host Mike Finnerty that donations of cash, supplies and gifts have been overwhelming.
The eight-year-old boy's parents Karine Desrochers-Gauthier, 32, and Patrick Gagnon, 37, died along with his siblings, Laurie, 4, and Felix, 2, when their apartment caught fire on Dec. 23.
Since then, Mathis has received video game consoles, karate and summer camp scholarships and more than enough clothing and toys. That's on top of money being collected by the regional fire department and put into a trust for Mathis.
More than $50,000 has been raised so far. Donations are still being accepted at the Saint-Zotique and Les Coteaux town halls.
Now Rhodes and Sélina Richard, the founder of the Community Wings charitable organization, are focused on getting any and all school fees, uniform costs and school supplies Mathis will need once he returns to school.
Rhodes said Mathis is now living with his aunt and uncle and their children, and will be transferring to a new school after his family's funeral next weekend.
Rhodes is requesting that anyone who wishes to donate a gift not wrap it, considering his family died right before Christmas.
Struggling with loss
The death of the young family has been difficult for Rhodes as well, who knew Desrochers-Gauthier since childhood.
“This is very hard for me. We were good friends. We grew up together," Rhodes said.
She said she was devastated to know a cigarette may be the cause of the fire. She said Desrochers-Gauthier and Gagnon had for years tried to quit smoking.
Rhodes said she keeps in touch with Mathis's aunt for daily updates on the boy.
She said she was profoundly touched by a photo the aunt posted online of Mathis smiling while feeding her baby.
"I just saw the picture and i started to cry," Rhodes said.