St. Louis University chess coach and grandmaster Alejandro Ramirez is under investigation by U.S. Chess officials for sexual assault and harassment of at least one person: a U.S. women’s chess champion who went public with the allegations on Wednesday.

Jennifer Shahade, a two-time women’s champion and a program director for U.S. Chess, said in a Twitter post she was sexually assaulted by Ramirez on two occasions a decade ago, and in recent years has heard from multiple women with similar accusations.

“When it was just me I didn’t feel like I had an obligation to report it,” Shahade said in an interview Thursday night. “When it turned out that it affects younger people … I felt ethically compelled to bring my experiences to light to help bring credibility to their stories.”

The allegations threaten to be the second national chess scandal centered in St. Louis in less than six months,…