In Hargitay’s new documentary, ‘My Mom Jayne,’ which premiered at the Tribeca Festival on June 13, her siblings recount the moment they were pulled to safety from the wreckage only to realize she had been left behind

Mariska Hargitay (left) and her film’s promotional poster.Credit : Craig Barritt/Getty; HBO

When Mariska Hargitay set out to make a documentary about her mother, she knew the project would inevitably tell the story of her own life, too.

My Mom Jayne, which marks Mariska’s feature film directorial debut, premiered as part of the Tribeca Festival on June 13 at Carnegie Hall in New York City. In the film, Mariska, 61, discovers through a conversation with her brother, Zoltan, that she was accidentally left behind at the scene of the car wreck that killed their mother, Jayne Mansfield, in 1967.

“I often think about why she didn’t just stay in the backseat with us?” Zoltan wonders aloud in a scene from the film, recalling how Mansfield had been arguing with her then-boyfriend, Sam Brody, and had decided to move up to the front of the car with him while the kids slept in the back.

“But I remember her comforting me, telling me I was going to be fine. 20 minutes later, half an hour, I heard her scream so loud, and that was it,” an emotional Zoltan continues.

Jayne Mansfield holding six-weeks old Mariska Hargitay in March 1964.Getty

Mariska’s eldest brother, Mickey Hargitay Jr., remembers the aftermath of waking up in a car with a blonde-haired woman who had helped rescue the children.

“It felt like my skin didn’t move, because it was bloody all over,” he recalls, adding that he thought he saw Mansfield in the front seat, but when that woman turned around to look at the boys, he realized it wasn’t his mother.

Zoltan was the one, however, who, upon waking up in the car, looked around and realized his little sister wasn’t present. He asked where she was, which led the adults to realize that they were missing the third child involved in the accident.

Back at the scene, Mariska, then only 3 years old, was pulled from the wreckage, where she had been lodged under the passenger seat with a head injury, explains her stepmom, Ellen Hargitay.

“Thank God Zolie woke up,” Ellen says.

Mariska, who was raised alongside her brothers by their father, Mickey Hargitay, also revealed in the film that her biological father is a man named Nelson Sardelli.

Sardelli, who is still alive and in his nineties, joined Mariska at the New York City premiere, as did Mariska’s sisters, Giovanna and Pietra Sardelli, and her eldest sister, Jayne Marie Mansfield.

“This is my story to tell,” Mariska told PEOPLE at the movie’s Tribeca Festival debut on Friday. “I had a rough time with the fact that somebody else told it before I did, and that was the impetus of the movie — that I wanted to tell my story.”

Adds the actress, “I encourage a lot of women, and men, to tell their stories,” explaining that the feeling is “empowering” and “gives ourselves back parts of ourselves.”

“I feel like this has been sort of divinely protected, that it hasn’t come out in the world,” she said. “And so it’s like I was protected until I was ready to tell my story.”