Zach Sobiech's battle with cancer may have ended, but the inspirational message he put out for millions will surely endure.
The 17-year-old high school senior from Stillwater, Minnesota recorded the song "Clouds" and posted it on YouTube last December, where it has been watched more than 3 million times since.
Sobiech died Monday, May 20, the Children's Cancer Research Fund reported. He had been diagnosed with the rare bone cancer osteosarcoma in 2009 when he was 14 years old, according to the organization.
Osteosarcoma is a bone tumor that usually develops in teenagers when they are growing rapidly, often around the time they are 15 years old. The condition is also seen in adults over 60.
It can occur in any bone, but often the tumors are found in the shin, thigh and upper arm, according to the National Institutes of Health. Chemotherapy is often prescribed to shrink the tumors, with surgery removing the rest of the tumor while saving the affected limb. Prognosis worsens once the cancer has spread to other parts of the body.
Sobiech underwent a hip replacement, hours of physical therapy, four major chest operations called thoracotomies, several minor surgeries, biopsies and months of chemo since his diagnosis, according to his website on the Children's Cancer Research Fund. By May of 2012, he found out the cancer spread to his pelvis and lungs, and he was given a terminal diagnosis.
Sobiech told CBS Minnesota last December. "You just didn't really want to accept it. You are in complete denial."
He turned his attentions to his music, and wrote and recorded "Clouds" as a thank you to everyone who stood by him during his cancer battle.
"That's me expressing my feelings," Sobiech said. "Every time I listen to it I go back to yeah, that's right, all these people are here for me."
He added, "With my situation you don't have time to be sad or angry or anything. You have to just go because you don't have that much time."
Sobiech also earned a recording contract with music giant BMI for his song.
Earlier this month, when Sobiech was faced with only weeks to live, celebrities including Brian Cranston, Sarah Silverman, Rainn Wilson, Chris Pratt, Anna Faris and Jason Mraz released a celebrity version of "Clouds" where stars sing along to the catch tune,
Throughout his rise to fame, Sobiech worked to raise money for the Zach Sobiech Osteosarcoma Fund.
"There was something unique in Zach, in the way he approached it with maturity, with grace, with a sense of humor. And he said it many times - it wasn't about him," John Hallberg, CEO of Children's Cancer Research, told CBS Minnesota on Monday.
Sobiech was also featured in a documentary from SoulPancake called "My Last Days: Meet Zach Sobiech."
The Children's Cancer Research Fund has more information on Zach Sobiech.
Here is Sobiech with his hit, "Clouds":