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The US Chess Federation reacted immediately to the Safe Play complaint from the U.S. Chess Championship and temporarily suspended Grandmaster Christopher Yoo’s membership, pending a full investigation.
Christopher Yoo was expelled from the tournament after a gross violation of both the St Louis Chess Club’s code of conduct and the US Chess safe play policy. Yoo teared up his scoresheet and struck a videographer.
Chief Arbiter Chris Bird clarified that “the videographer was not at fault, nobody approached Yoo as he left the playing room, the punch was completely unprovoked, from behind and in no way accidental.”
Update: St. Louis Metropolitan Police Confirmed Charge