I know this isnt as large of a scale, but I will use this example
A man who is charge of the building is watching the security cameras, when the power goes out in the city. The man saw a shadowy figure right before the power went out, it was the shape of a man, something shining in the left hand. This figure was right outside the main exit, the easy way out. He runs down the stairs and meets the people in the lobby. The man warns them, he tells about what is there. He gives as much proof as possible, he shows from around the corner there is a shadow and describes what he saw, the people listen. Many are skeptic and come up with other explanations for what he said. The man starts showing another way out, but it is much harder and very few use it. But it will promise they live, some follow the man. The skeptics decided he was not telling the truth and that there was no man outside. The man sends his son out there, to prove that it is no lie, the son comes back beaten, bruised, scarred. The skeptics were set in their mind though, although some did realize it was no lie take the other way. The rest keep going that way, saying that it could have been a number of things that happened to that man's son. They walk through the door to find out the figure was real. The skeptics are then kidnapped and the shadowy figure tortures them for the rest of their lives. The skeptics now know the truth, but only to late, the decision they made in that hour they were now paying for. They now regret the choice they made, but only after it is to late for them to be saved. The man never forgets them and is heartbroken they wouldnt follow him, but he cannot do anything now.