I think speculation is that at that moment you wither wished people to stay or go. The ones who people wanted gone, or felt that in that moment, left. Kevin wished to be with his family at that moment so they stayed. Nora was having a bad morning with her family and wished them gone. Hence the guilt. Maybe that is what the Guilty Remnant know. The leftovers sent them away.
I think that's a great theory...and would explain why Patty told Kevin right before she killed herself that she knew he understood why they were still there.
BTW, anybody catch the orchestral version of Metallica's "Nothing Else Matters" in the beginning of the episode in the scene where Jill was at the GR house with her mom and changed into white clothes?
I thought that was a pretty cool touch and a great version of the song.