Police found the bodies of three — all in their late teens or early 20s — inside the home on Sicard Street on Tuesday, after receiving a 911 call around 8 a.m. ET. Their names haven't been released.
The two 17-year-old boys, who were intercepted by police as they were leaving the home Tuesday, are due in youth court Wednesday. They can't be named under the Youth Criminal Justice Act.
"They were three violent deaths," said Trois-Rivières police Const. Michel Letarte.
Tearful family members were seen being escorted by police outside the crime scene Tuesday. Neighbours said the sisters' mother is away on vacation.
News of the homicide quickly reached students and staff at a local school where one of the girls was a student.
"The students heard the rumour and we were dealing with shock," said Réjean Lemay, principal of Collège Marie-de-l'Incarnation.
Lemay said grief counsellors were called in to help support students and staff.