Oscar Knox, a five-year-old boy whose battle against a rare form of cancer captured the hearts of thousands and united a community, has died.
The Co Antrim boy's brave fight against the disease was documented by his parents, Stephen and Leona, on Twitter and he soon became an online phenomenon after they launched an appeal, raising hundreds of thousands of pounds for treatment.
His parents announced his death to more than 53,000 followers of the Wee-Oscar Twitter account this morning with: "Our beautiful, amazing and much-loved son, Oscar James Knox gained his angel wings yesterday afternoon. Sleep tight little man Xx."
He was first diagnosed with neuroblastoma in November 2011, but was given the all clear in April 2013. Sadly, the disease returned in August that year.
His family's fundraising appeal raised the £250,000 needed to pay for immunotherapy treatment in America and his parents set up the Twitter account to allow family and friends to receive updates on his progress. The account quickly gained thousands of followers.
Their campaign won many high-profile friends and memorably Oscar wreaked havoc during a visit to the offices of Northern Ireland's First Minister Peter Robinson and Deputy First Minister Martin McGuinness at Stormont.
The political leaders led the tributes today. Mr Robinson said his thoughts and prayers were with his parents and sister Isobella.
"Their sense of loss and devastation is immeasurable," he said.
"When I met Oscar I was struck by his infinite energy and sense of fun. He had a tremendous capacity to overcome the challenges he and his family faced together.
"Oscar was an amazing little boy who lived his life to the full and filled those around him with admiration and hope. He will be deeply missed by everyone who met and loved him."
Mr McGuinness said: "Oscar touched the hearts and minds of everyone and inspired countless people through his positive attitude and resilience.
"The day Oscar and his family visited Stormont was one of my most uplifting days in politics and you couldn't help but be enthused by his vibrancy and spirit."
Oscar was an enthusiastic Celtic supporter but his campaign was also backed strongly by Glasgow Rangers fans.
When Celtic played Belfast side Cliftonville in Glasgow last summer in a Champions League qualifier Oscar was the team mascot.
Celtic chief executive Peter Lawwell said: "This is absolutely devastating news and our thoughts and prayers are with Oscar's parents, Stephen and Leona, and his little sister, Izzie, at this desperately sad time.
"We can't even begin to understand the pain of their loss, but I hope that there will be a small measure of consolation in knowing that there was genuine love and affection for Oscar from the Celtic family throughout the world.
Additional reporting by PA