"What upset me the most about hearing these stories [was] that obviously [his behavior] was grossly inappropriate, but also it just seemed so callous," Couric told People. "And that's not the Matt I knew. There's a duality in human beings, and sometimes they don't let you see both sides."
In November 2017, Lauer was fired from "Today" after a female colleague made a detailed complaint accusing him of inappropriate sexual behavior. Multiple women came forward with sexual misconduct allegations against Lauer following his dismissal.
In her new book "Going There," Couric wrote of another incident where an unnamed female producer confided in her about an alleged email Lauer, who was married at the time, sent asking her to "butter him up" using her thighs and requesting she wear a "skirt that came off easily" to his office.
"I remember being shocked and disappointed," Couric said of the incident to People. "If I had to do it again, I would have made sure that young woman was okay."
Despite sharing anchor duties on a hit morning show for years, which involved a vast amount of time spent together, Couric said she wasn't as close to Lauer as people might believe.
"I think it's hard for people to understand that we didn't share intimate parts of our lives with each other," she explained. "I could count on one hand the times that I talked to him as I would a confidant or a really close friend."
"Our offices were next to each other, and so I think when he engaged in this kind of behavior, he was extraordinarily secretive about it," she added.
And even though she considered him a "player," Couric said he never brought up the subject of his bad boy reputation. "He was a flirt. Certainly I read that he was unhappy in his marriage. But, honestly, I never had that discussion with him," she added.
She went on to say it took her a very long time to come to terms with the claims against Lauer. "Also, to appreciate the damage that was done to women who were taken advantage by many powerful men."
Couric said she no longer speaks with Lauer and that she doesn't know if he can or will find redemption, adding, "It's really not for me to forgive him."
"This is Matt's story, and it's the story of the people he exploited."
The National Sexual Assault Telephone Hotline -- 800.656.HOPE (4673) -- provides free, 24/7 support for those in need.