Credits: ROB LAMBERTI/QMI AGENCY
He has been identified as Tyson Bailey, Det.-Sgt. Justin VanderHeyden said at the scene.
Police are searching for two men, one white and one black, both between 25 and 30 years old, VanderHeyden said.
Bailey didn't live at the building but was not previously known to police, he said.
A call was made to police shortly after 2 p.m. for the shooting at a social housing building in the Regent Park neighbourhood.
"When officers arrived on the scene they found a teenage boy suffering from life-threatening injuries," Const. Tony Vella said. "He was shot multiple times in his body."
The mortally-wounded youth was rushed to hospital where he was pronounced dead soon after.
Vella said the boy was found in the hallway on the 13th floor of the highrise.
"One of the elevators was stuck at that floor with its door open," he said, adding investigators are still trying to determine if there is a connection between the slaying and the lift.
Toronto Fire Services say emergency crews ascended to the 13th floor using stairs and brought the victim down the same way because of issues with the elevators, which were recalled to the lobby with firefighters' keys.
Toronto Fire spokesman Capt. David Eckerman said one elevator was inoperable after police exited at the third floor and had the doors close behind them.
Alyssa Archer, 21, said she moved in just months ago. Leaving a shelter bus after police allowed residents back into the building, the mother of two said she was shocked and fearful.
"I don't see why a 15-year-old would get shot, that's kind of outrageous," she said. "I don't think guns should be allowed in this city."
Sealand White, who was also only 15, and Jermaine Derby, 19, were executed at the same Toronto Community Housing Corporation building in the wee hours of Oct. 9, 2010.
The teens left a party in one of the apartments around 2 a.m. and as they exited the elevator on the ground floor they were riddled with bullets.
Their killer has never been caught.
--With files from Kevin Connor and Don Peat