Hearts are somber in Sag Harbor as residents mourn the loss of 12-year-old Katy Stewart of North Haven, who died Thursday morning after a battle with a rare form of liver cancer.

Katy's bright smile became familiar to East End residents after two Roar For A Cure benefits organized by The Max Cure Foundation raised funds and support for two families fighting fiercely to save their children from deadly cancers.

Katy, said Max Cure President David Plotkin, whose son Max survived his battle with lymphoma,* "fought with courage and bravery, always wearing a smile." The Roar For A Cure carnivals, he added, lent support to Katy's parents, Jim and Brigid, so they "would be able to dedicate time and energy on getting Katy well," while providing some normalcy for their young son, Robert, during the times that Katy underwent treatment.

"As parents, and as a community, everyone rallied around Katy," Plotkin said. "Memorial Sloan-Kettering did everything they could to cure her. Unfortunately, the cancer was too strong."

Katy , a seventh grader at Pierson Middle School, passed away in her sleep, only days before the New Year.

"Early this morning as the sun was rising in pink hue over the harbor, our beautiful and beloved daughter and Robert's sister, Katy, became an angel in heaven," wrote the Stewart family in a message on CaringBridge.org, a website devoted to sharing news of those who are facing health challenges.

"She was a special gift to the lives of those who knew her, a kind and thoughtful child who was a giving and generous soul," the message continued. "She was a magnificent blessing to our lives and words can't really express just how we much we loved her so."

Katy's parents are familiar faces on the East End — her father, Jim, teaches at East Hampton High School and her mother, Brigid, is assistant principal at the Montauk School.

Her heartbroken family also thanked the community for reaching out to them during their darkest hours. "You made our journey lighter, and touched Katy's heart in so many ways. Please say a prayer for her. She will be with us always."

As news spread of Katy's passing, those who knew her reached out with words of support — and memories of the little girl who touched their hearts forever.

"The Sag Harbor Board of Education would like to send our heartfelt condolences to the Stewart family at this difficult time," said Chris Tice of the Sag Harbor School Board. "Katy was a very special girl, loved by so many in our community. She will always be remembered for the beauty and light of her spirit.

"We will remember Katy as a bright, hard working student with many gifts and talents," Tice continued. "All who knew Katy appreciated her radiant smile and kind, generous spirit."

"Her life brought great joy to all who knew her," said John Gratto, superintendent of the Sag Harbor School District. "The Sag Harbor school family admires the grace and courage Katy and her family demonstrated during her illness. Our deepest condolences are offered to the Stewart family during this time of grief and remembrance."'

Katy, a little girl who loved horses and was bright, talkative and full of life, melted hearts at the Roar For A Cure carnivals with her vivacious personality, despite the fact that the first year she was in a wheelchair and too ill to enjoy the festivities. Last year's event saw her enjoying the activities that were planned in an effort to find a cure for her rare hepatoblastoma.

"She was a star when I first met her and will be my shining star forever until we 1meet again one day," Plotkin said. "We share the same birthday, Sept. 1, a day that will no longer be just a birthday to me."

Viewings are scheduled for Tuesday and Wednesday, from 2 to 4 p.m. and 7 to 9 p.m. both days, at Yardley and Pino Funeral Home in East Hampton.

A funeral is scheduled for Thursday at 10:30 a.m. at St. Andrew Church in Sag Harbor, followed by a reception in the church hall.

In lieu of flowers, the family requests that donations be made to the Max Cure Foundation, and designated either to a scholarship fund to be established in Katy's memory at Pierson High School or to pediatric cancer research in memory of Katy at Memorial Sloan Kettering Cancer Center. The donations are tax deductible with 100 percent of the donations going to either of the designated causes. Checks should be mailed to the Foundation at 21 Settler's Lane, Westfield, New Jersey 07090.  The scholarship will be awarded to students who exemplify remarkable courage, kindness and empathy.

*An earlier version of this article incorrectly stated the type of cancer that Max Plotkin survived. He survived lymphoma, according to his father.