A teenager was stabbed and suffered critical injuries after a verbal altercation between two groups escalated Monday night in Dollard-des-Ormeaux.
Police say the suspects had sticks, pepper spray and at least one edged weapon when they confronted a group of young people on Balko Street.
"The suspicious group probably pepper-sprayed everyone in the other group before stabbing one of them with an edge weapon," said Const. Yannick Ouimet.
Several neighbours called 911 to alert police.
The victim is in hospital in stable condition.
Police said investigators interviewed friends of the victim who were at the scene, but they were unable to provide a complete description because the suspects wore scarves covering their faces.