The loss of power hit at the worst time for Canada's largest city - the afternoon rush. Nowhere was that more acutely felt than Union Station, the city's transportation nexus.
Hundreds of subways, regional commuter trains and commuter buses converge on the station every day.
By six o'clock pm, the cavernous interior of the building buzzed with activity under the dim glow of the back-up lights.
On the GO concourse, throngs of commuters queue each day to take trains to the sprawling bedroom communities around the city. Today it was different.
In the variety stores lining the corridors of the cavernous building, merchants worked at a feverish pitch, selling cold drinks and candy bars by candlelight.
Closer to the platforms, commuters huddled around electronic display boards to check on the status of their trains. A collective groan arose when it was announced all trains were cancelled due to the power outage.
"We cannot communicate with our trains," was the announcement. Although the trains are diesel-electric, the switches are powered by the electricity grid, as is the communication system.
Just steps away, the doors to the TTC platforms were locked and all commuters cleared. At street level, thousands of people stood, speaking on cell phones, waiting for buses and lining up at hot dog carts.
Shariq Zameer was among the many waiting for a bus. He was at work in an office tower when the outage hit.
"It was chaos," he said. "I had to walk 30 floors down to get out," said the Mississauga resident, sweating in the late-day heat. "I came to get the GO bus and it's not happening," he said. "I can't even walk back home."