Sun told City's website: "The ball was in our penalty area and had crossed from to the where I was. I turned around, chased the ball with McSheffrey, and it was in front of me.
"He went for the ball and tried to obviously push me, but I just used my shoulder for a 50/50, maybe 51 in my favour!
"I tried to do my job as normal. When I heard the whistle, I thought he was diving maybe, but the referee pointed to the spot.
"I thought; 'Oh my God, I can't believe it.' Sometimes when you are sad, you cry, but it was more than that. I could not believe it - even somebody who knows a little bit about football wouldn't think that was a penalty.
"I couldn't do anything about it so I had to walk away - it's the only thing I could have done and that decision killed the game off for us."