"There is no right reason to shoot someone directly in the face," said Camille Godbout of student protest group ASSÉ.
The incident was captured on video by a Huffington Post reporter.
In the video, students can be seen approaching police outside the National Assembly Thursday evening, following the release of the provincial budget. The Huffington Post gave CBC/Radio-Canada permission to use its video.
The video shows some shoving between police and students before tear gas is fired into the crowd.
At least one person was hit directly by the tear gas, including a young woman whose face was injured.
Godbout said police didn't have to fire the tear gas directly at protesters to disperse the crowd.
"They're shooting directly at people instead of shooting, for example, in the air," she said.
Officers trapped protesters and prevented them from leaving the premises after the gas was released, she said. Many protesters were seen getting their eyes rinsed out by friends and fellow students.
Police defend use of tear gas
A Quebec City police spokesman told CBC's Daybreak Friday morning that officers only launched the tear gas after physical altercations broke out.
"I will not comment on the video, because you see the first time they start to advance, and then they charge the policemen, and you know tear gas is used to avoid body-to-body confrontation and to disperse the [protesters]," said François Moisan of the Quebec City police.
He said police would review the events of Thursday's protest, adding the officers used a type of tear gas at this particular event that does not launch the entire canister — just the cap.
The young woman was treated in hospital.
Radio-Canada is reporting her mother is considering a lawsuit.