"You must’ve housed a tormented heart”: The open letter to Kate Spade that’s gone viral.

Earlier this week, designer Kate Spade was found dead in her New York City apartment.

It’s understood that she took her own life.

55-year-old Kate’s sudden death came as a shock to her friends and family – as well as her customers.

Canadian woman and fan, Heather Delaney, has perfectly encapsulated her love of Kate Spade and her designs in a heartwarming open letter to the designer.

The letter, which has since gone viral on Facebook, describes Heather’s experience of taking her five-year-old daughter to purchase her first Kate Spade design.

Four years ago, on a family vacation, Heather decided to take her daughter Elle for her “very first Kate Spade experience”.

“The night before, I couldn’t sleep. My husband would laugh as we laid there in the bed, me jumping with excitement, in anticipation of her and I getting matching bags the next morning. This was a serious mama dream come true,” Heather wrote.

Heather planned to get a full-size Kate Spade bag and buy a matching crossbody design for her daughter Elle, but when they got to the store the next day, their plans changed.

Heather showed Elle design after design, but none of the bags appealed to her daughter – until she saw a pair of furry black earmuffs.

“Then, she saw it. The first Kate Spade item that she would call hers,” Heather wrote.

“Her face would light up, and her eyes would go wide. She fell in love…”

“Does anything scream ‘Canadian’ more than going into a Florida store, and buying a pair of earmuffs?!” Heather joked.

Heather added that she wished Kate could have seen how much their purchase of furry black earmuffs had made Heather and Elle smile.

“Kate, I’m sorry that we could not bottle that up for you,” she wrote.

“I’m sorry that we could not bottle up every grin, every laughter, every happy heart that walked through your stores. I’m sorry that we could not gather every smile that you put on a humans face, whether it was because they just found the most loveliest brooch for their wedding day, the most exquisite pair of earrings to wear on their Graduation Day, or even the most coziest pair of earmuffs to wear around Florida… And lay those smiles in your lap.”

"I’m just so sorry you were sad, while you made so many others happy. So incredibly happy."

Heather also wrote about the guilt she felt when she heard of Kate's death.

"You must’ve housed a tormented heart, Kate. And that breaks mine."

"I’m sorry, Kate, that we could not gift you the happiness that was felt in this six year olds body that day. Sat in that Kate Spade store. With her Kate Spade ‘cozy’ earmuffs.  I kinda feel guilty now for feeling so much happiness that day, wondering now if you were perhaps sad that day," she continued.

She signed the open letter as "a forever fan of yours".

Kate Spade is survived by her husband entrepreneur Andy Spade and her 13-year-old daughter Frances Beatrix Spade.

If you are experiencing crisis you can always call Lifeline on 13 11 14.