Sen. Kamala Harris, D-Calif., said Wednesday it was "very painful" when she learned a longtime staff member had settled a $400,000 harassment and retaliation lawsuit against another one of her former employees.

Larry Wallace, who worked for Harris when she was California's attorney general, was accused of "gender harassment" by his former executive assistant in December 2016 while he was Harris' Division of Law Enforcement director. Danielle Hartley's suit was settled in May 2017 by Harris' successor, Xavier Becerra, though the California Justice Department denied Hartley's allegations as part of the agreement.

Wallace, however, didn't resign until last December after Harris received media inquiries about the matter. He had been serving as a Sacramento-based aide for the senator.

"First of all, it was a very painful experience to know that something can happen in one's office — of almost 5,000 people, granted — but that I didn't know about it. That being said, I take full responsibility for anything that has happened in my office, I always do and I always will. The buck stops with me," Harris told CNN on Wednesday. "Even in the office of someone who has been an advocate for women and women's rights, and all people's rights, there's no office that is immune from this kind of behavior. And that's something that we're also going to have to deal with, and it is a sad statement."

Harris has faced renewed scrutiny over Wallace's alleged misconduct after she referenced him in The Truths We Hold: An American Journey, a memoir she released Tuesday. In the book, the California Democrat praises Wallace for his "leadership" while creating an "implicit bias and procedural justice training program."

Harris is openly mulling running for president.