Shannon Tavarez, the 11-year-old Broadway actress who starred in the hit musical "The Lion King," died Monday after a long battle with acute myeloid leukemia. Known for visiting and helping other cancer patients, Rihanna took to her Twitter to send condolences to the family of the young star.

"Just got off of a plane ride and got horrible news that our little star Shannon [Tavarez] has lost her battle against leukemia! Way too soon ... keep her family in your prayers," Rihanna tweeted on Tuesday.

Diagnosed with leukemia in April, Tavarez had difficulty finding a bone marrow match because of her mixed ethnicities (African-American and Hispanic). Rihanna and Alicia Keys attempted to raise awareness for the performer by encouraging fans to register as donors.

"[Tavarez] should be performing on Broadway, but is confined to her bed, fighting for her life," the singer told People in July. "She needs to find a bone marrow donor to survive. I urge all my fans to register [as donors]. It's the most beautiful thing someone could do, to give the gift of life."

Despite their efforts, doctors were unable to locate a suitable bone marrow donor. In August, they took a different approach as the performer underwent an umbilical-cord blood transplant at Cohen Children's Medical Center in New York.

Tavarez's mother, Odiney Brown, appreciated the support and condolences in a statement, saying, "Shannon's strength and her happy, positive spirit will live on in our hearts and minds each day.

Shannon's dream was to perform onstage, and that she did. It is our hope that Shannon's legacy will continue to inspire other brave children battling leukemia. We are grateful for the outpouring of love and prayers."

In addition to the R&B singers, 50 Cent and Tony Yayo also joined the cause, filming a PSA for the "Get Swabbed to Save a Life" project.

Earlier this year, another cancer patient, Jasmina Anema, to whom Rihanna had remained close, also lost her fight against leukemia.