What happened during the Magic - Celtics Game 5 where an yst walks off the set?

I was watching the game, then it cut to the 3 commentators (Reggie Miller, a white guy, and a black guy I believe) and I hear the black guy stand up, say some things, and walk out, and the other 2 ysts (Miller and white guy) look shocked and comment on the man's sensitivity. This was on TNT, what happened? Who walked off? Why?