Christopher Yoo was put in check.
The 17-year-old chess grandmaster was arrested and expelled from the U.S. Chess Championship in St. Louis on Oct. 16 after hitting a woman when he lost a match to four-time champion Fabiano Caruana, the St. Louis Metropolitan Police Department told NBC News.
In a video shared to YouTube Oct. 17, Yoo was seen crumpling up his scoresheet, stuffing it in his pocket and storming out of the tournament hall following his loss. And while his exit wasn't caught on camera, the Saint Louis Chess Club said in a statement that he proceeded to "strike a videographer from behind" on his way out.
"The Saint Louis Chess Club immediately provided assistance to the videographer," the club's statement shared to X (formerly Twitter) Oct. 16 continued, "and called the police who responded."
And the tournament officials also took action against Yoo, who was charged with a misdemeanor of fourth-degree assault by authorities before being released back to one of his parents in accordance with the Juvenile Courts, officials told NBC News.
"Chief arbiter Chris Bird expelled Yoo from the tournament due to gross violations of our code of conduct and the U.S. chess safe play policy," the Saint Louis Chess Club explained before noting that the organization "fully supports this decision and has banned Yoo from the club."
"Yoo's results from rounds 1-5 will be annulled, and the tournament standings will be adjusted accordingly," the club continued. "Players scheduled to face Yoo in the remaining rounds will receive a bye, granting them an additional rest day."
The club added, "We take player conduct seriously and do not tolerate violations of our standards. We acted swiftly to address this situation, ensuring a respectful and safe environment for everyone involved in the tournament."
Following the incident, Yoo—who became the youngest American master at 9 years old in 2016 and the youngest International Master at 12 years old in 2019—apologized for his actions at the tournament, calling his behavior a "serious mistake."
"I am really sorry for hitting the videographer," Yoo wrote in a statement shared to his parents' Facebook Oct. 21. "I was disappointed losing the game to Caruana and lost my temper. That’s no excuse, I know."
He added, "Every day I wish I could go back in time and undo it, but I can’t."
Noting that he accepted the consequences, the teen went on to promise to "be better from now on."
"Best of luck to Caruana. I am sorry this happened after our game," he continued. "And best of luck to the other players and best wishes to the St. Louis Chess Club."
And his parents echoed his apology to the videographer in their own statement, expressing their concern for Yoo's unexpected lash out.
"Something like this has never happened before," they wrote in an Oct. 19 statement on Facebook, "and he will be getting therapy to help make sure his mental well-being is properly cared for and that something like this will not happen again."
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