A medical examiner in suburban New York says the estranged wife of Robert Kennedy Jr. died of asphyxiation due to hanging.

Mary Richardson Kennedy, 52, an architect known for her philanthropic and environmental work who also was hit with drug and alcohol charges in recent years, was found dead Wednesday afternoon on the family's property in Bedford.

In a statement issued by Robert Kennedy Jr.'s chief of staff, the family described Mary Kennedy as "a genius at friendship."

"Mary inspired our family with her kindness, her love, her gentle soul and generous spirit," the family said.

Her death came after several hard years for the family. Her husband, Robert Kennedy Jr., a prominent environmental lawyer and the son of Sen. Robert F. Kennedy, had filed for a divorce in 2010. The two had married in 1994 and had four children together. The divorce case was still pending.

Both the Richardson and Kennedy sides of the family expressed sadness over her death in public statements that noted her "gentle soul and generous spirit," her work advocating environmentally responsible building designs, and her deep love for her children.

"We deeply regret the death of our beloved sister Mary, whose radiant and creative spirit will be sorely missed by those who loved her," the family said in a statement. "Our heart goes out to her children who she loved without reservation."

The family hasn't commented publicly on whether she had struggled with depression, or why she might have taken her own life.Her family cited her devotion to her children in remembering her.

Neighbor Leslie Lampert, who owns the Cafe of Love restaurant a short drive from the Kennedy home, said Mary Kennedy was "at all times just a lovely individual."

"She was community oriented," Lampert said. "She was always kind in our presence."

Another neighbor, Kim Fraioli, a trauma therapist who lives a few houses down from the Kennedys, said the family was private.

"We left them alone," Fraioli. "We didn't have any interaction. I think it's a tragedy. It's very sad for their family and the surviving children. My heart goes out to the family."

At the home on Wednesday, a red brick mansion with a columned porch entrance set in a heavily wooded acreage, police kept media away.

Mary Richardson had known the Kennedys for years, through her friendship with Robert Kennedy Jr.'s sister, Kerry Kennedy, whom she met at boarding school. She had been Kerry Kennedy's maid of honor at her wedding in 1990.

She had had trouble with drugs and alcohol and had two high-profile arrests around the time her husband filed for divorce in 2010. She was arrested twice by police officers who suspected her of driving while intoxicated. Her license was suspended once, but a drunken driving charge was dismissed. Last July, a judge dismissed a charge of driving under the influence of prescription drugs, saying she hadn't been aware it could impair her ability to drive.

At the time of her sentencing, famous family and friends spoke out in support of her.

Her mother-in-law, Ethel Kennedy, wrote in a letter that she "is a caring, nourishing mother who has nursed her four children through lifelong bouts of debilitating allergies," according to an account in Westchester's The Journal News at the time.

Kerry Kennedy, in her letter, said, "When I look at my three daughters, my wish for them is that they are as blessed as I have been to have a companion, a confidante, a friend, like Mary Richardson."

Mary Kennedy grew up in Hoboken, N.J., the daughter of a professor at the Stevens Institute of Technology. She had two brothers and four sisters.

Her own family had been intertwined with the Kennedys even before her storybook wedding aboard a boat in the Hudson River Valley in 1994. She met Robert's sister, Kerry Kennedy, at boarding school when they were teenagers, and was a maid of honor at her wedding to Andrew Cuomo, now governor of New York, in 1990. Mary's eldest sister, book editor Nan Richardson, was also involved in human rights causes with Kerry Kennedy, now divorced from Cuomo.