The news of his death was posted on a website that chronicled his journey.
The message about his death was posted as a journal entry by a woman who identifies herself as Aunt Mimi. It reads in part, "Heavens gates opened for our beloved William at 4:22 this morning. He was with his loving parents, Amy and Mark. The illness can no longer constrain our angel William; he has spread his wings, taken flight, and will be free of pain and suffering for all eternity."
Earlier this month, the Raleigh Police Department honored William by making him the department's youngest officer.
In a statement Thursday, Raleigh Police Chief Harry Dolan said: "William will be remembered by all who had the privilege to know him for his cheerful nature and for the heroism and dignity he displayed in the face of extreme adversity. We will forever cherish the honor of having him among our ranks."
The Raleigh Police Department said Bunn would be buried with full police honors. The funeral is set for Saturday July 3.
ABC11 Eyewitness News Anchor Barbara Gibbs spoke to the Bunn family in April about a 5K charity run for William. The Bunn Fun Run and Walk for neuroblastoma research and the William Bunn Fund was held on May 1.
William, a first-grader at Douglas Elementary, was diagnosed with neuroblastoma in 2007 at the age of five and had undergone two bone marrow transplants and numerous surgeries during his treatment.
"William is amazing he would come in every morning just full of energy and he has this eagerness to learn," first grade teacher Heather Starritt said.
Neuroblastoma is a cancer that develops from nerve cells found in several areas of the body. It usually arises in and around the adrenal glands, which have similar origins to nerve cells and sit atop the kidneys.
However, neuroblastoma can also develop in other areas of the abdomen and in the chest, neck and pelvis, where groups of nerve cells exist. Neuroblastoma most commonly affects children age 5 or younger and is the most common cancer in babies. About 650 children are diagnosed with Neuroblastoma each year in the United States according to the American Cancer Society.
For more information about this cancer, click here.
During William's treatment, the cancer went into remission for eight months, but recently returned. The 8-year-old spent the last part of his life at home under the care of his parents with the assistance of a hospice nurse.
The family will receive friends on Friday, July 2 from 6 p.m. to 9 p.m. at New Hope Baptist Church, 4301 Louisburg Road in Raleigh. Funeral services will be held at New Hope Baptist Church on Saturday, July 3 at 11 a.m. After the service, William will be laid to rest at Raleigh Memorial Park, 7501 Glenwood Avenue, Raleigh. Funeral arrangements for William are being handled by Brown-Wynne Funeral Homes.In lieu of flowers, memorials may be made to the V Foundation for Cancer Research, St. Baldrick's Foundation, and neuroblastoma research.