A 30-year veteran professor of Stanford University’s School of Medicine—who was fired after an investigation into his alleged sexual misconduct—apologized this week in a letter that attributed his behavior to cultural differences between his native Colombia and “evolving” social norms in the U.S.

Jose Montoya was fired May 30 for what the school called “multiple violations of the university’s conduct policies,” and it was first reported this week by The Stanford Daily.

According to an anonymous statement to the newspaper by “a group of individuals affected by his conduct,” a “large group of women” who worked under Montoya came forward in March with “extensive allegations of sexual misconduct, assault, and harassment.”

“The allegations included multiple instances of Dr. Montoya attempting unsolicited sexual acts with his female employees, among many other instances of harassment and misconduct, and were confirmed in an investigation,” said the statement.

Stanford claims that after it received the complaints, the school “promptly initiated an investigation led by an outside attorney and Stanford faculty member,” which verified the violations, a spokesperson said this week.

In his apology letter, Montoya wrote that “what has unfolded since March has been a huge surprise and devastating to me and my family.”

The prominent researcher, who studies chronic fatigue syndrome and the disease toxoplasmosis, said he was surprised to learn that members of his team “experienced some of my behaviors as attempts at unsolicited sexual acts, harassment, and misconduct.”

“It is extremely important that you know I have not been involved in any sexual or romantic relationships with employees, trainees, colleagues, or CFS team members,” he added. “I have mentored, supported, and facilitated the professional growth of both female and male team members in numerous other Stanford communities and the Toxoplasmosis laboratory for almost three decades. I have done this with respect, professionalism, and the affection proper of my Hispanic heritage—without any other expectation than that of an advisor who is proud to see their mentees advance and succeed.”

“The social norms in the U.S. are evolving and quite different than those from my culture and homeland,” Montoya continued. “I did not sufficiently appreciate that difference. It is my responsibility to change and be both mindful and respectful of the boundaries of personal space—and I pledge to do just that.”

“To my ME/CFS patients and their family members, mentees, colleagues, and friends, I’m sorry I have let you down,” he added.