About 90 minutes after the protest began police declared the demonstration illegal and moved in to break up the crowd.
Officers fired tear gas and a photographer captured one officer firing at a woman from about two metres away.
The projectile hit the woman in the chin, leaving her with a one large cut and about a dozen smaller wounds.
She was reportedly taken to hospital for treatment.
Public Security Minister Lise Theriault said she was disturbed when she saw that video and wants to hear from police.
"As a mother, when you see something like that, if it’s my son, or my girl, when people go to demonstrations, they have the right to protest, but safely,” said Theriault