My manager was to be in an interview panel for selecting a person for a role senior to mine (I won't be reporting to). Since he could not make it I was requested to be on the panel which I obliged. It turns out the first candidate is actually internally applying and had actually interviewed me.
He was my official buddy at the start, just a few months back. I talk to him on a weekly basis, though we do not collaborate on much. It is a weird situation for me. And potentially for him.
What is the optimal way to deal with this scenario?
Note that I would be interviewing only this candidate. My manager would be available for the others.