A Concordia student who has previously filed a lawsuit against the Montreal police claims she was injured when an undercover police officer pushed her at a protest Friday.

Katie Nelson, a seasoned protester, says the small demonstration escalated quickly. She says she saw a group of masked men dressed in black street clothes, and one had his mask down. When she looked closely, Nelson said she recognized the man as one of the officers named in the lawsuit she filed a few years ago against nearly 20 Montreal police officers for alleged political profiling, physical and sexual harassment during a number of protests.

“I realized it was him and just started screaming, ‘This is a cop, this is a cop’ and he was swearing at me,” she said.

She turned and saw someone masked running at her from behind and says she was violently shoved.

“It clicked that [the person was] a cop too and I was on the cement, I couldn't stand up, I couldn't move.”

She was taken to hospital by ambulance with a concussion, a swollen knee and an injured wrist that now seems to be dislocated.

Montreal police say nelson was not targeted and they can't confirm her version of events.

“Paramedics told us one female was suffering because she tripped on the floor but what happened we don't know exactly at this moment,” said Montreal police Cmdr. Ian Lafreniere.

Lafreniere confirmed officers in civilian clothes were used because some protesters were throwing rocks and causing damage.

But Nelson says she's had it and will wait until she heals to decide her future path as a protester.