Toronto police Constable Jenniferjit Sidhu told AFP "a person armed with scissors or a knife" busted into a fifth floor office in a building in the city's north end.
"Two to five people in the office were injured," she said. One victim was rushed to hospital with serious injuries.
A suspect -- a man in his 30s -- has been arrested, she said, adding that a heavily armed emergency response unit has secured the building.