There were rumors about the events you speak of among the death knights. I always expected the story to be more... symbolic.
We must warn others, but we must be discreet. As soon as the Lich King knows we're making our move, he'll move the location of the heart -- we'll never get a chance like this again.
We have to speak to Tirion Fordring and his Argent Crusade.
Heavy words, <name>. If it were somebody else saying them, I'd be likely to judge them insane.