A source tells ET that the late Kate Spade had become withdrawn from friends and family before her death, leading many of them to worry about her well-being.
Spade was found dead in her Manhattan apartment of apparent suicide on Tuesday, and there was a note left, the NYPD confirmed to ET. CBS News reports the designer left a suicide note addressed to her 13-year-old daughter, Frances, telling her it was not her fault.
Spade was 55 years old.
"Kate definitely seemed to distance herself recently and her family was worried about her," the source tells ET. "She ventured out less and less and some friends began to wonder what was wrong. People who were used to hanging out socially with her started to worry about her because she was nowhere to be seen."
"Kate's suicide has been extremely heartbreaking and has left some friends confused because she kept a happy persona in public for so long," the source continues. "But those that knew her well, knew she suffered for years with depression."
Kate Spade through the years
Kate Spade through the years
Kate Spade during The 2001 VH1/Vogue Fashion Awards - Arrivals at The Hammerstein Ballroom in New York City, New York, United States. (Photo by Jim Spellman/WireImage)
Kate Spade during The Fresh Air Fund Salutes American Heroes at Tavern on the Green in New York City, New York, United States. (Photo by Jim Spellman/WireImage)
Designer Kate Spade arriving at the 2002 Ace Awards presented by The Accessories Council at Cipriani 42nd Street in New York City. November 5, 2002. Photo by Evan Agostini/ImageDirect.
Kate Spade during The Concert for New York City - After Party at Hudson Hotel in New York City, New York, United States. (Photo by Ron Galella/WireImage)
Kate Spade during 13th Annual Glamour Magazine's Women of the Year Awards - Arrivals at Metropolitan Museum of Art in New York City, New York, United States. (Photo by Dimitrios Kambouris/WireImage)
Kate Spade with husband and brother-in-law David Spade at the 20th Annual American Fashion Awards at Avery Fisher Hall, Lincoln Center in New York City. 06/14/2001. Photo: Evan Agostini/ImageDirect
Kate Spade during 17th Annual CFDA Awards at JP Morgan Atrium in New York City, New York, United States. (Photo by Ron Galella/WireImage)
Designer Kate Spade is photographed at her offices. (Photo by David Howells/Corbis via Getty Images)
Kate Spade and Andy Spade during Costume Institute Benefit Dance: 'Party of the Year' - Arrivals at Metropolitan Museum of Art in New York City, New York, United States. (Photo by Dimitrios Kambouris/WireImage)
Kate Spade during 14th Annual GLAMOUR Women of the Year Awards - Red Carpet at American Museum of Natural History in New York City, New York, United States. (Photo by Dimitrios Kambouris/WireImage)
Kate Spade (Photo by Carley Margolis/FilmMagic)
Kate Spade during CFDA 7th on Sale Kick-Off - Red Carpet and Inside at Sky Light Studios in New York City, New York, United States. (Photo by Rabbani and Solimene Photography/WireImage for LaForce and Stevens)
NEW YORK - JUNE 7: Designer Kate Spade attends the '2004 CFDA Fashion Awards' at the New York Public Library June 7, 2004 in New York City. (Photo by Evan Agostini/Getty Images)
Kate Spade, Andy Spade and Ruth Lande Shuman, founder/president of Publicolor (Photo by Carley Margolis/FilmMagic)
David Spade and Kate Spade during Photographer's Gallery Presents Slim Aarons Curated by Kate Spade at Fred Segal Cafe in West Hollywood, California, United States. (Photo by Chris Weeks/WireImage)
NEW YORK CITY, NY - APRIL 30: Kate Spade and Andy Spade attend PARSONS The NEW SCHOOL FOR DESIGN 59TH ANNUAL BENEFIT and FASHION SHOW Honoring SUSAN D. KRONICK, Vice Chairman, Federated Department Stores, Inc. at Grand Hyatt on April 30, 2007 in New York City. (Photo by JIMI CELESTE/Patrick McMullan via Getty Images)
NEW YORK, NY - NOVEMBER 10: Kate Spade attends the 2015 Basser Center For BRCA Benefit at Cipriani Wall Street on November 10, 2015 in New York City. (Photo by Daniel Zuchnik/WireImage)
NEW YORK, NY - APRIL 28: Kate Spade speaks on stage at Build Series Presents Kate Spade and Andy Spade Discussing Their Latest Project Frances Valentine at Build Studio on April 28, 2017 in New York City. (Photo by Monica Schipper/WireImage)
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According to the source, Spade "tried desperately to hide" her stuggle with depression.
"She truly cared about her brand and didn't want the public to know of her pain," the source says. "Kate's suicide has made some friends question what they could have done to change the horrific outcome. She definitely hid the truth of her intense suffering from so many friends, and in turn they had no idea she needed help."
The source notes that Spade's loved ones' main concern is now for the well-being of her beloved daughter, whom she shared with her husband of 24 years, Andy.
"Right now we are all looking for answers and are so worried for her young daughter," the source says. "Kate loved her daughter so much, but clearly couldn't endure the pain any longer."
Reta Brosnahan Saffo, Spade's older sister, told CBS News that she believes the designer was suffering from bipolar disorder. Saffo said that she "tried numerous times to get her help."
"It finally took its toll on her," she wrote in an e-mail to CBS News. "A very tragic and sad ending to the life of a very colorful and delightful being."
"Fuzzy picture but I love it," he shared on Instagram alongside a touching photo of the two together. "Kate and I during Christmas family photos. We had so much fun that day. She was so sharp and quick on her feet. She could make me laugh so hard."
"I still can't believe it," he continued. "It's a rough world out there people, try to hang on."
“Knowing Katy, this is how she would want to be remembered," Brosnahan wrote. "She had a light that words can’t capture but touched everyone she came into contact with. She was exceedingly kind, beautifully sensitive, insanely talented, funny as heck and one of the most generous people I have ever known. She was effervescent. “Hug your loved ones extra tight today.”