I was at Penn and watched this happen. I wasn't paying the closest attention, but it sure looked like he got pushed. I thought it was Kenya that he was trying to slip by on the inside, maybe it was some other country, but he got forcibly shoved back. He didn't literally get thrown off the track, though - it seemed like he just got kind of pissed and let himself get knocked out the next time somebody touched him. So I'm pretty sure the tantrum was in response to somebody playing rough and not just him tripping over himself or something like that.