Saoirse Kennedy Hill's Cause of Death Revealed After Being Found Unresponsive at Family Compound

Robert F. Kennedy‘s granddaughter Saoirse Kennedy Hill died this summer of an accidental overdose, PEOPLE confirms.

The Cape & Islands, Massachusetts, district attorney, Michael O’Keefe, said in a news release on Friday that she died from “acute methadone and ethanol toxicity in combination with other prescription medications.”

Citing her death certificate made available Friday, The Boston Globe, The Boston Herald and local TV station WCVB reported that Saoirse had alcohol and a mix of drugs — diazepam, fluoxetine, methadone, nordiazepam and norfluoxetine — in her system. Diazepam and fluoxetine are the generic versions of Valium and Prozac. Methadone is commonly used to treat opioid addiction.

The daughter of Courtney Kennedy Hill and Paul Hill, Saoirse was found unresponsive on Aug. 1 in grandmother Ethel Kennedy‘s home on the family’s Massachusetts property. She was taken to a nearby hospital and pronounced dead, authorities have said.

She was 22.

RELATED: All About Saoirse Kennedy Hill’s Irish Childhood — and Her Trip Back Before OD: ‘She Might Have Been Better Off Staying’

At her memorial, her uncle Robert F. Kennedy Jr. remembered her sleepless night of adventuring — in celebration of the completion of a college paper — before she was found dead. He said she saw the sun rise on the last morning of her life, having spent the previous hours in “a flight of her characteristic exuberance” out and around Hyannis Port.

There was singing, there was dancing and there was swimming at dawn.

In bed, Saoirse was already thinking about a planned trip to Los Angeles, her uncle said at her funeral. Instead, she “woke up with God.”

A rising senior at Boston College, where she was expected to return in late August before graduating next year, Saoirse has been remembered by friends and family as a bright, warm young woman with the drive to see how the world could be changed for the better.

But she had her own challenges, including grappling for years with depression. In 2016, while still a high school student, she opened up in an essay for her student paper about her mental health.

“People talk about cancer freely; why is it so difficult to discuss the effects of depression, [bipolar], anxiety, or schizophrenic disorders?” she wrote. “Just because the illness may not be outwardly visible doesn’t mean the person suffering from it isn’t struggling.” But the students could change that.

“Let’s come together to make our community more inclusive and comfortable,” she wrote.

RELATED: RFK Jr. Shares Private Family Photos of Niece Saoirse Kennedy Hill

“Saoirse was fierce, both in her love for her family and yearning for justice,” her uncle Robert F. Kennedy Jr. wrote on Instagram after she died, along with several family photos of her. “A fearless adventurer, she inspired curiosity and daring in her friends. But her greatest gift was to find humor in everything and to give us all the gift of her laughter — and our own. The gaping hole that she leaves in our family is a wound too large to ever heal.”

Saoirse was involved with starting the Deerfield Students Against Sexual Assault at her private school, Deerfield Academy, according to the school paper. She also participated in a March for Our Lives rally in 2018. At Boston College, where she enrolled after Deerfield, she became vice president of the College Democrats.

“In classes she was often the first student to offer an opinion on readings that demanded clear critique about the challenges of contemporary society,” one of her professors, Marcus Breen, told The New York Times.

Saoirse Kennedy Hill | Kerry Kennedy/Instagram
Saoirse Kennedy Hill | Kerry Kennedy/Instagram

RELATED: Kennedy Family Remembers Saoirse Kennedy Hill’s Final Hours

Kerry Kennedy (left) and niece Saoirse Kennedy Hill
Kerry Kennedy (left) and niece Saoirse Kennedy Hill

Bernadette Rivera previously told PEOPLE she remembered sitting next to Saoirse on a flight from Washington, D.C., to Connecticut about a year and a half ago. Saoirse greeted her with a “big smile” and a hello.

“One of the things that was definitely clear is that she was a very caring person, really sort of interested in the world and in the condition of humankind and trying to understand why certain things are the way that they are … and looking for ways to make it better,” Rivera said.

They talked about family, about politics, “and what was so fascinating is she was genuinely curious about the state of the world,” Rivera said.

Saoirse “didn’t openly say she suffered, but she did say that she had troubles and that she wasn’t as confident about herself as people initially thought,” Rivera said. “She recognized that she had so much to be grateful for, but it didn’t always feel that way.”

RELATED VIDEO: Saoirse Kennedy Hill’s Father Paul Overcame His Fears to Pay Tribute to His Late Daughter

In a statement soon after she died, the Kennedys said they were “shattered.”

“Her life was filled with hope, promise, and love,” the family said. “She cared deeply about friends and family, especially her mother Courtney, her father Paul, her stepmother Stephanie, and her grandmother Ethel.”

Saoirse “lit up our lives with her love, her peals of laughter and her generous spirit,” the Kennedys said.

Said grandmother Ethel, 91: “The world is a little less beautiful today.”