CNN  — 

A granddaughter of Robert F. Kennedy died of an accidental overdose, according to her death certificate filed Friday in Massachusetts.

Saoirse Kennedy Hill, 22, was the daughter of Courtney Kennedy Hill, one of the 11 children of the late presidential candidate and Ethel Kennedy, the environmental and human rights activist.

Kennedy Hill had acute methadone, diazepam, nordiazepam, fluoxetine, norfluoxetine and ethanol toxicity in her system at the time of death, according to the toxicology results revealed in the death certificate.

First responders were called to a medical emergency at the Kennedy compound in Hyannis Port, Massachusetts, at 2:30 p.m. on August 1.

Kennedy Hill was pronounced dead at Cape Cod Hospital at 3:14 p.m, according to her death certificate.

A Boston College communications student, Kennedy Hill was due to graduate next year, the college said after she died.

She had volunteered in Mexico to build schools in indigenous communities and was “moved by the causes of human rights and women’s empowerment,” her family said in a statement released after her death.

“She lit up our lives with her love, her peals of laughter and her generous spirit,” the family’s statement read.

Kennedy Hill had previously written an opinion piece for her high school newspaper about her struggles with depression.

“My depression took root in the beginning of my middle school years and will be with me for the rest of my life,” she wrote in a column in the Deerfield Academy’s student publication in February 2016. “Although I was mostly a happy child, I suffered bouts of deep sadness that felt like a heavy boulder on my chest.”

CNN’s Bob Crowley, Carolyn Sung, Nicole Chavez and Kevin Liptak contributed to this report.