Authorities responded to the scene and discovered the vehicle "had run into the bus platform at Westboro station", which resulted in numerous injuries on the bus and platform, according to police.
Ottawa police chief Charles Bordeleau said the bus driver was arrested at the scene and taken in for questioning, but he declined to provide further details.
Three people have been killed and 23 others injured, some of them critically, when a double-decker bus crashed into a bus shelter at Westboro station in Ottawa in the middle of a Friday evening rush hour.
The Ottawa Hospital said shortly after 8 p.m. that seven patients were in critical condition.
"I want to send my deepest condolences to the families of victims and everyone affected by today's tragic bus crash", Prime Minister Justin Trudeau tweeted.
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Bus crash at Westboro Station on the Transitway in Ottawa. Two of the three people killed in the crash were on the bus, while the other was standing on the platform at the time of the collision.
The driver was detained at the scene and he was set to be interviewed by police.
The investigation will take a long time and likely will mean the closure of the busway and nearby roads for at least many hours, Bordeleau said. Another was wheeled on a gurney in obvious distress, wailing loudly enough to be heard on an overpass above. Bordeleau said the Ottawa Paramedic Service and Ottawa Fire Services worked the scene in partnership with the Ottawa Police. "I saw one person being lowered from the top floor in a seated position".
"Based on the way it looked, if there was anybody at the front of the bus at the top ..."
"I haven't seen something of this magnitude before", he said. "My first thoughts are with those who have been injured and their families". "I have asked staff to ensure all necessary resources are made available to assist them through this hard time", he said.