A little girl who called herself Mrs Bieber and had a pretend wedding to the pop star as she battled a rare form of brain cancer has died.
Avalanna Routh, who suffered from an typical teratoid rhabdoid tumor, a fast-growing tumor of the brain and spinal cord that usually occurs in young children, died on Wednesday morning.
Physicians and nurses at the Boston hospital where she was treated had previously organised a pretend wedding between the six-year-old and Justin Bieber.
The ceremony, where Avalanna wore a t-shirt which said 'Future Mrs Bieber' and stood next to a portrait of the singer, sparked a social media campaign to help her meet the star.
Bieber later arranged for the youngster to meet him in New York, where they spent a couple of hours together before he tweeted that the experience was inspiring and the best thing he's ever done.
He has now taken to the social networking site to mourn her death:
Dr. Charles Roberts of Dana-Farber/Children's Hospital Cancer Center, where Avalanna received treatment, said she was diagnosed with cancer when she was 18-months old and although she had responded to initial treatment, the cancer had kept coming back.