What are the rules for determining the traitor in Betrayal at House on the Hill?

In Betrayal at House on the Hill, the traitor is determined when a specific event triggers the haunt phase of the game. This event is usually related to the actions or decisions made by the players during the game. Once the haunt phase begins, a specific scenario is revealed that designates one player as the traitor, who then works against the other players to achieve their own objectives.