Dozens of people stood outside their father's home on De Blois Street in Boucherville, on Montreal's South Shore.
It's there where their lifeless bodies were found early on Friday morning.
"He was a very good friend. I'm shocked," said Yannick Ouellet, who had known Jérémie since elementary school.
The young men's violent deaths are being deeply mourned by those in the community.
Investigators with the provincial police are working with a murder-suicide hypothesis. The body of the young men's father, Michel Dubuc, was also discovered in the home.
The father's connection to a shooting in Terrebonne that killed two people — lawyer Benoît Côté and notary Marie-Josée Sills — is still under investigation, as well.
The 21-year-old Jérémie and 19-year-old Gabriel were well-loved, said vigil organizer and family friend Caroline Gosselin.
They are survived by mother, France Ainsley.