Hailey Roser got the surprise of her life when pop star Justin Bieber flew to Milwaukee, Wis., to visit the cancer-stricken superfan. Bieber’s road to Hailey began when the young fan’s parents started a social media campaign in hopes of getting the singer to visit their 4-year-old daughter, who was diagnosed with a rare, cancerous brain tumor in August, the Journal Sentinel reports. A "Healing Hailey" campaign was launched online, with Indiegogo collecting almost $15,000 in donations for the family. The social media push worked, and the 18-year-old pop star met with Hailey at Milwaukee’s BMO Harris Bradley Center.