It's been 15 years since Mischa Barton's character Marissa Cooper was killed off on "The O.C." and the actress finally opened up about why.

Speaking with E! News, Barton said she previously felt "ashamed" to discuss what led to her departure in the season 3 finale.

"I've always felt ashamed in a way to really talk about what went on behind the scenes because I've always been a very private person and very aware of people's feelings," she said. "Now that we're living in this era where we do speak out about our experiences and women do come clean about what was really going on behind the scenes and how they were treated, it's a slightly different thing."

The 35-year-old revealed that talks about her leaving the series began shortly after season 1, when they decided to add Rachel Bilson to the main cast and after encountering "bullying from some of the men on set that kind of felt really s-----."

Barton explained that things got to be "too much" for her halfway though season 2 when they started "doubling up on episodes."

"I look back on it pretty fondly, but there's stuff I think people did wrong and the way they handled it," she said. "So, I just didn't feel I could keep going."

That's when Barton said producers offered her the option of her character being killed off or leaving room for a potential comeback. At that time, she was getting offers to headline "big films" but had to turn them down, despite it being her dream, which is why she ultimately chose to close the door for good.

"It just felt like it was the best thing for me and my health and just in terms of not really feeling protected by my cast and crew at that point," she explained.

"The O.C.," created by Josh Schwartz, aired on Fox for four seasons between 2003 and 2007. It starred Ben McKenzie, Adam Brody, Rachel Bilson, Peter Gallagher, Kelly Rowan and Melinda Clarke alongside Barton.