Two males were rushed to a trauma centre on Sunday afternoon following an apparent double stabbing.
Paramedics say they were called to 220 Oak St. at 12:29 p.m.
One of the victims was without vital signs at the time of transport and paramedics say he had been stabbed at least six times.
The second victim had a single stab wound and was in serious but stable condition.
Toronto police reported that a suspect had been taken into custody. Charges are pending, police say.
Sgt. Dan Powell told reporters that officers have recovered a small, edged weapon. Police are not seeking any other suspects, he added.
Powell said police were called to the address for a reported fight.
"That's how the call came to us; it was involving three people involved in a fight," he said.
Powell said police had cordoned off a scene near a park bench, as well as a scene in the main lobby of the building.
The sergeant said the suspect had been arrested on the 17th storey of the building at 220 Oak St.