This. Exactly this. That same feeling took me by surprise as well. I had no idea I could have such depth of pain for a loss of someone in my life, let alone a therapist. I still think it hurts more than it should, too.
However, I also know (at least intellectually), that it's a "normal" response. At least a common response, since I'm not sure the word "normal" ever really applies.

It will take time to heal and for the pain to subside. It's similar to losing a spouse or anyone else that you are very close to.

Give yourself time to grieve. It's ok to feel the emotions so you can work to get past them.
Give yourself the kindness you would give to anyone who was grieving a loss of a loved one.
You always have us at PC to lean on for support!