Thang. That is so cool.
You must have been quite excited when that happened? I assume this is a first for you.
How long did the event go on for (minutes, Hours)? I know you eat, sleep next to the tank so was it lucky timing to be there?
I experienced something similar (but nothing close). I had a PencilUrchin, and one day, it climbed to the top of rocks and released a ton of eggs while I was watching it's odd climbing behavior. I ran to get my camera but it ended before I got back.
But for your SPS to do this is quite amazing? What is just the one coral?
Congrats on catching the moment. You are famous in my mind.