Having quickly seen this question, I'll respond by saying that I don't think any of us, this side of the grave, really know. It is a mystery! Consider, how do you respond when somebody asks this same question about God?
God knows all things from all Eternity. God IS all knowledge, and all being, and all Eternity. In redeeming us, Christ makes it possible for us to share in the Divine Life of God. His Saints, people who have "fought the good fight" and have now been raised to the fullness of Life in God, undoubtedly know and do things all of us are incapable of understanding.