The U.K. boy Charlie Proctor, whose battle with cancer touched millions around the world, died on Friday night after telling his mother, “I'm sorry for this.”

The 5-year-old boy who hailed from Church, U.K, 240 km north of London, died in his parents’ arms nearly three years after being diagnosed with a rare type of cancer.

His parents, Amber Schofield and Ben Proctor, had raised $611,600 in a last-ditch effort to pay for a life-saving treatment in the United States. But they’d been told Charlie’s cancer had become incurable and that he was too sick for treatment, which would have included a liver transplant.

On Saturday, his mother wrote a post on the family’s Facebook page that, “my best friend, my world, Charlie, took his final breath” the night before.

She said the world had “lost an incredible little boy” and called Charlie her “best friend” and “biggest inspiration.” She said Charlie had inspired thousands of people around the world, including famed singer, Pink.

Schofield thanked Charlie for not only showing her what “love really means” but because “you gave me chance to be a mum.” She wrote about how the couple’s “ hearts are aching” and how she was “hurting so much.”

But she wrote that, “now, it’s time to fly, I am so, so proud of you. You fought this so hard.”

Charlie was diagnosed in February 2016, with Hepatoblastoma, a rare cancer that starts in the liver. After undergoing successful surgery at Birmingham Children’s Hospital in the U.K, his cancer went into remission.

Unfortunately, his cancer returned and his story attracted attention around the world thanks to his parents’ efforts to raise money for his treatment.

Hours before her latest post, Schofield wrote another in which she declared it was the “last photo I post of Charlie.” She described how her son’s weight loss, a symptom of the cancer, had made Charlie unrecognizable.

“Where has my chunky baby gone? ... He was the cuddliest baby ever! He’s our chunk. I want everyone to remember Charlie for who he is,” she wrote.

His mother went on to talk about how her memories of him being funny and cheeky were replaced with the daily struggles of him sad, tired, fed up and depressed.

“‘I don’t know what to do anymore” are his main words.. today, he’s been very agitated, wanting to lay down, sit up, lay in bed, then on the beanbag, then on the sofa,” she described in excruciating detail.

“Charlie, at one point, turned to me and said in the most quiet, panting voice, ‘Mummy, I’m so sorry for this’,” his mother wrote. “He was sorry because he wanted to move again and he felt he had to apologize for that?”

She talked about how her heart broke upon hearing that from her son. She said “no child should feel the emotions Charlie is feeling. Having to watch them deteriorate in this way is the most painful thing anyone will ever feel.”

Despite Charlie spending his last few hours in her arms, she asked: “How can I miss him so much when he’s led (sic) beside me? I miss just having a chat, a cuddle that doesn’t cause pain. I miss squeezing him and kissing him all over.”