Det. Sgt. Daniel Nielsen told CBC News that shortly after 6:30 p.m. ET on Saturday, tenants on the ninth floor of the building at 100 Harrison Garden Blvd., near Yonge Street and Highway 401, were made aware that a person was in medical distress.
"A resident or a visitor in an apartment on the ninth floor approached a couple of other tenants on the ninth floor and asked them to call 911 as his friend was in medical distress," Nielsen said in a telephone interview on Sunday.
When paramedics arrived, "they found the 28-year-old male victim suffering from an apparent gunshot wound," Nielsen said.
"They rendered medical assistance, but his vital signs were absent and he was pronounced dead at the scene."
Nielsen said investigators have yet to identify the man who had asked the others to call 911, as he left the building before paramedics arrived. But he said police would like to speak to him.
Investigators have been reviewing video surveillance from cameras inside the building.
“What we have learned is that shortly after this occurred, there were four to five males that left the building,” said Nielsen.
"One of them, I believe, is the male that had gone and asked for assistance from neighbouring tenants."
Nielsen later said there is no indication the men seen leaving the building were involved in what happened to the victim, but investigators want to talk to them.
“I’d like them to come forward on their own. At this point, there’s no information that they’re involved. So I’d like to speak to them,” he said.
“If they have any concerns, they can contact a lawyer and have the lawyer contact us.”
On Sunday afternoon, police identified the victim as 28-year-old Hussein Hussein.
Nielsen said the victim is known to police.