Zach Sobiech, the 18-year-old star of an internet video that went viral, passed away early Monday morning surrounded by friends and family.

In the past few weeks, donations to Zach's cause, the Children's Cancer Research Fund, increased immensely, as did downloads of his song, "Clouds," which has more than 2.9 million page views on YouTube.

Several celebrities took to YouTube a few weeks ago to record a tribute to Sobiech, who has had cancer since he was 14 years old.

Check out Zach's song "Clouds", the celebrity tribute, and a documentary about Zach here.