Avalanna Routh, the 6-year-old who captured the world's heart after spending a day with pop star Justin Bieber, has died from an extremely rare form of brain cancer. 


"Our darling Avalanna went to Heaven this morning. Oh Avalanna, the brightest star -- you took our hearts with you, our greatest Love," her parents posted early Wednesday on Twitter.


Routh made headlines in February after Justin Bieber flew her and her family to New York City to spend an entire "Valentine's Day" date in the Big Apple. According to MSNBC, the two played board games, signed autographs for each other, and Avalanna even was "able to lay her hands on the famous Bieber hairdo and style it her own way."


The dream date was the culmination of a massive social media campaign by Avalanna's family to put the young girl and Bieber in the same room. So in love was the girl with the 18-year-old pop star that friends and family threw her a "Bieber Wedding" with a cardboard cut-out of the star and a T-shirt that read: "The Future Mrs. Bieber."


Justin later tweeted that the experience was one of the best things he had ever done, adding: "... she was AWESOME! Feeling really inspired now! #MrsBieber." That hashtag later when on to become a worldwide trending topic on the social media network.


Upon hearing the news today, Bieber tweeted"one of the greatest spirits i have ever known is gone. please pray for her family and for her. RIP Avalanna. i love you."


Bieber also promoted a link to Cure AT/RT Now, a community dedicated to supporting families of children with atypical teratoid rhabdoid tumors. 


You can watch Avalanna's inspiring story, produced for the "2012 Stand Up To Cancer" telecast, below. 


Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Justin Bieber mourns loss of cancer patient 'Mrs. Bieber'
Avalanna Routh, who took on the nickname of "Mrs. Bieber" after receiving a dream date with pop star Justin Bieber, died early Wednesday morning (Sept. 26).