At 1:07 p.m., the following tweet appeared from The Associated Press: "Breaking: Two Explosions in the White House and Barack Obama Injured."
Reaction on the stock market was swift, as what had been a mildly positive day on the Dow Jones quickly turned negative, with America's benchmark stock index losing more than 134 points or more than a full per cent of its value in a matter of seconds.
Within minutes, it had become clear that the report was untrue, and the result of AP's account being hacked. White House spokesperson Jay Carney told journalists at a press briefing in Washington, "The president is fine. I was just with him."
Twitter moved to suspend AP's account until the agency could regain control of the account.
That caused an equally swift reaction, with the Dow regaining everything it had lost and then some within 10 minutes of the original tweet.
Reports suggest more than $20 billion worth of equity positions changed hands on the New York Stock Exchange during the brief trading hiccup.
The TSX was relatively unscathed, with Canada's benchmark stock index losing about 35 points in the aftermath of the report before gaining it all back and then some.
Toward the end of the trading day, the S&P/TSX composite index was at 12,086, virtually unchanged on the day.