The 55-year-old co-founder of her namesake brand, Kate Spade New York, had reportedly been suffering from manic depression in recent years, but David had no idea how much she had been struggling with the mental illness.
According to multiple sources, Spade also left behind an emotional suicide note, addressing her 13-year-old daughter, Frances Beatrix.
"She was actively seeking help for depression and anxiety over the last 5 years, seeing a doctor on a regular basis and taking medication for both depression and anxiety".
The New York police department announced on Tuesday that Spade had been found unresponsive in her bedroom at home that morning.
Saffo and other members of the Spade family tried in vain to get Kate help, but she says that, ultimately, Kate's pain was too great.
In an e-mail her older sister, Reta Saffo, said she believed Spade suffered from bipolar disorder, writing, "It finally took its toll on her".
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"We were best friends trying to work through our problems in the best way we knew how", it adds.
"We ate many meals together as a family and continued to vacation together as a family", Andy says. The contents of that note, as well as the physical state of the apartment and the comments of the witness, lend to the credibility that it is an apparent suicide, ' he said.
Kate Spade speaks to the crowd during an event at Hall's on Grand at Crown Center Plaza on Wednesday, March 9, 2016 in Kansas City, Mo.
Spade told National Public Radio (NPR) a year ago that she first discussed starting a handbag company with Andy Spade while they ate at a Mexican restaurant in 1991.
Spade's niece, "The Marvelous Miss Maisel" star Rachel Brosnahan, was also among those paying tribute to the fashion maven. "This was someone that really valued her private life and I don't think Kate could live in the cruel world that we live in today".
While many remember Kate Spade for her fashion empire, the designer hoped it wouldn't be her only lasting legacy. She was pronounced dead at the scene at 10:26 a.m., The Times said. "We honor all the beauty she brought into this world". "Buying a Kate Spade handbag was a coming-of-age ritual for a generation of American women", The New York Times wrote.