LOS ANGELES (AP) — The chancellor of California State University, the nation’s largest public university system, has resigned after accusations that he mishandled sexual misconduct allegations.

Joseph I. Castro resigned on Thursday, effective immediately, said the CSU Board of Trustees.

In a statement, Castro called it the most difficult decision of his professional life.

Castro fell under criticism after an investigation by USA Today published Feb. 3 questioned the handling of misconduct complaints against Frank Lamas, former Fresno State vice president of student affairs, while Castro was the university’s president.

The article said that Lamas was the subject of a series of informal complaints including allegations beginning in 2014 that he improperly touched women, made sexist comments and harassed or retaliated against workers.

No action was taken against Lamas until a formal complaint was filed in 2019, when he was barred from campus and later found to have violated a CSU harassment policy, according to documents cited by the San Francisco Chronicle.

Lamas denied the allegations and appealed the finding. He retired in 2020 as part of a settlement agreement. Under the agreement, he received a $260,000 payment and while he was barred from ever working at CSU again, Castro agreed to write him a letter of recommendation to help find work elsewhere, the documents indicated.

The revelations sparked a protest by Fresno State students earlier this month.

Steve Relyea, CSU’s executive vice chancellor and chief financial officer, will be acting chancellor until an interim chancellor has been named, the board said.

The Cal State system is the largest four-year public university system in the country with 23 campuses, 477,000 students and 56,000 faculty and staff, according to its website.

Castro, appointed in 2020, was the first Mexican American and native Californian to lead the CSU system.

“I have been honored to serve the California State University for more than eight years, including as its eighth chancellor, and the decision to resign is the most difficult of my professional life,” Castro said in a statement. “While I disagree with many aspects of recent media reports and the ensuing commentary, it has become clear to me that resigning at this time is necessary so that the CSU can maintain its focus squarely on its educational mission and the impactful work yet to be done.”