After Canada fought back from 3-1 in the final two minutes of the third to send the game to overtime, the referees called a penalty on Ottawa Senators defenseman Thomas Chabot just over five minutes into the extra frame.
Finland would score on the ensuing powerplay and win the gold medal. It's incidents like this that make officiating in the NHL playoffs more exciting to watch. When the refs put their whistles away, in a sense, so games aren't decided like this.