Zach Sobiech, who wrote a song about his cancer called "Clouds" that became a hit on YouTube, passed away due to the terminal disease on Monday. Sobeigh was 18 years old.

When his song, Clouds, about his cancer became a viral hit, he was just 14. He was diagnosed in 2009 with osteosarcoma, a rare bone cancer. Sobiech had been told he had a year to live last May, and he did just that. He had several other songs that went viral, mostly in the form of goodbye songs to friends and family members.

Stars covered Zach Sobiech's song in a tribute video that appeared on Rainn Wilson's SoulPancake YouTube channel. The stars who appear in the video include Ashley Tisdale, Colbie Caillat, Anna Faris, Jason Mraz, Sara Bareilles, Jenna Fischer, The Lumineers, Rachel Bilson, Ed Helms, Phillip Phillips and others.

Many celebrities and fans mourned Sobeigh. SoulPancake released a documentary about Zach Sobiech and his life for their series "My Last Days". Another popular song was entitled "Fix Me Up".

A statement on his death from the Children's Cancer Research Fund said that

""Zach's life ended just as he lived, embraced by the love of his family, friends, grace and music."

"Zach was at home and at peace with those he loved most," the statement read.

Supporters mourned his passing and donated to cancer research in his name. Sobeich's family asked that in lieu of flowers, supporters donate to Zach Sobiech Osteosarcoma Fund in order "to help carry on Zach's mission to help kids with cancer."