What I know of Justice is primarily what I have heard from Isabela. Her explanation indicated that his...presence is what influenced you to do what you did.
I was at Kirkwall before and after these events. The Divine sent me to see if an Exalted March would be a necessary to suppress the growing Mage-Templar conflicts, and then afterwards when Cassandra and I tried to locate Hawke. Varric was the only one left of your group.