NEW WESTMINSTER, B.C. -- Police believe a man who pushed a woman at Columbia SkyTrain Station Thursday evening had stepped in to break up a dispute and did not mean for her to fall into the path of an oncoming SkyTrain, seriously injuring her.

According to New Westminster police, an altercation between two women who did not know each other broke out after a dispute about a seat on the platform just after 6 p.m.

When the argument between the two women turned physical, police say, a 24-year-old man who did not know them stepped in to try and break it up, when he was then attacked.

"She was then pushed by the male. The victim then stumbled back, and fell onto the SkyTrain tracks and an inbound train that was in the process of coming to a stop," Acting Insp. Andrew Perry with the New Westminster Police Department said Friday.

The 32-year-old woman was trapped under the oncoming SkyTrain, where she sustained serious but non-life-threatening injuries, including “significant” injuries to one of her legs.

The 24-year-old man stayed on scene and was taken into custody. He has since been released. The Major Crimes Unit is leading the investigation, and so far police have seen one angle of surveillance video that showed the push.

“At this time there is information the man acted in self-defence and did not intend to push the female onto the tracks. Hence, that factored into our decision making on whether or not there are grounds to believe an offence had occurred at this point in time,” Perry said.

CTV News asked if the man who pushed the woman had stepped in as a Good Samaritan when he intervened between the two women.

"That appears to be the case right now," Perry said.

Mike Tumu witnessed what happened.

"She was throwing punches at him and coming at him, and he was kind of putting his hands up, and i think just with the motion she tripped on herself," Tumu told CTV News Thursday night. "People were screaming, crying, trying to figure out what to do, how to get out.

New West police don’t believe drugs or alcohol were factors, but the investigation is ongoing and they are looking into whether mental health may have played a role.

Police are asking anyone who saw what happened to contact investigators, noting that the incident was also traumatic for those who witnessed it

They say support services through a victim assistance unit are available for those who may need it.

"Please don’t feel you have to go this alone," Perry added.

A bus bridge was set up Thursday night as police investigated along the platform, but the station has since reopened.

Police are looking to speak with any additional witnesses as part of the investigation, including the second woman involved in the original argument, and anyone else who may have cellphone video that shows what happened.