Sparring one time with a blue belt who had just returned from Brasil. I outweighed him, and managed to get him into mount and trapped both of his arms under my knees. The match had gotten a little intense and about half the class was gathered around watching us roll. Everyone was shouting advice at both of us. One of the purple belts yelled at me to go for a collar choke since his arms were pinned. As I went for that, the instructor told my opponent to upa out. He bucked really hard and since my center of gravity was leaned forward and both of my hands tied up in his collar, my forehead was slammed into the mat and everything went black. Luckily I regained consciousness a second or two later, and my body had gone limp and still kept him down long enough to keep mount.
