(CNN)One of Molly Shannon's most famous "Saturday Night Live" characters was awkward, clumsy, Catholic school student Mary Katherine Gallagher.
In an interview with Los Angeles Times, Shannon explained how the character came to be after a tragic car accident resulted in the death of her mother, sister and cousin when the actress was 4 years old.
"I was very heartbroken and very sad and just trying to hold it all together as a kid," she said. "There's no way that you could feel that type of deep pain about your mother and your sister being dead, so you just hold it all in, and it comes up later in life."
The accident critically injured Shannon's father, who was driving under the influence.
In character as Mary Katherine Gallagher Shannon would literally throw herself in the role, sometimes hurting herself in the process.
She said she was so into it that she would sometimes wake up the next day confused as to why she was bruised and battered.
"I didn't care if I cut myself or I made myself bleed," Shannon said. "I did not give a s—. I looked at it like punk rock. I was reckless, and because of what I went through, I just didn't care about anything."
These days she's busy with work on shows including "The White Lotus" and "The Other Two" as well as her forthcoming biography.
Sharing her story makes her feel vulnerable, she said.
"You feel like you put your heart right there on the table, but I hope that my story can help other people," she said.