Zach Sobiech used his songs to say goodbye to the world. The world, it seems, is still not quite ready to let go.

A few years ago, Sobiech was diagnosed with osteosarcoma, an aggressive form of bone cancer. Last year, around his 17th birthday, doctors told him that he didn’t have long to live. His mother encouraged Sobiech to write letters—and that’s how the song “Clouds” was born. The tune is catchy, the lyrics simple:

Well I fell down, down, down

Into this dark and lonely hole

There was no one there to care about me anymore

And I needed a way to climb and grab a hold of the edge

You were sitting there holding a rope.

And we’ll go up, up, up

But I’ll fly a little higher

We’ll go up in the clouds because the view is a little nicer

“We knew it would resonate with anyone within earshot,” says Kris Huson, a spokeswoman for the Children’s Cancer Research Fund in an interview with Quartz. But, “as a nonprofit, we don’t have the budget to amplify.”

The fund, though, partners with radio station KS95 in Minneapolis to fundraise, and executives there were captivated by Sobiech’s story. On Nov. 6, “Clouds” was recorded by Atomic K Records with a volunteer crew of musicians, a producer/mixer, and videographer Woolly Rhino to film the recording session. This video was uploaded to YouTube on Dec. 3:

The next step was to release the song digitally, but as the cancer fund’s Huson says, “our core competency is not releasing music.” Again, the nonprofit found a partner, a group called Rock the Cause to release the song in the busy Christmas season, promote it and book Zach and his band—called A Firm Handshake—for concerts.

On Dec. 14, CNN did a story on the song and video going viral, which was then broadcast on CNN Student—played into classrooms all over the country. Soon thousands of school kids were sending in their own versions of “Clouds.”

Other media outlets began picking up the story.

Things calmed down in February for a few months. Then on Zach’s 18th birthday, on May 3, a company called Soul Pancake released a documentary on YouTube, My Last Days: Meet Zach Sobiech. At 22 minutes long, it is not the type of video that is supposed to go viral. Think of the 30-second Harlem Shake, which prompted TechCrunch to explain: “A five-minute video? Ain’t nobody got time for that.” But millions have made time for this:

In conjunction with the documentary, Soul Pancake also launched a celebrity tribute video of “Clouds,” released just days later.

On May 20, after attending his prom, strumming his guitar one last time, receiving his high school diploma in a special ceremony, Zach Sobiech died.

For still many people though, his story was just beginning.

The left-leaning website Upworthy, which tries to make “things that matter” go viral, had written about Sobiech and his song before under the headline, “This Kid Is Going To Die. He Is Also Going To Rock. And He Needs Your Help.” Upon learning of his passing, writer Adam Mordecai began googling to learn more about the teen and came upon the longer documentary. Those of us who have watched it will not be surprised at Mordecai’s reaction—he wept. And then wanted to share it with everyone he knows. (Notably, Mordecai’s own father died of pancreatic cancer.)

His Upworthy piece links to the My Last Days video under the headline, “This kid just died and what he left behind is wondtacular.” Huson recalls: “That’s when things really went bonkers.” The package got more than 16.1 million page views and at least $90,000 donated through this link.

At the Personal Democracy Forum last week, Upworthy’s editorial director invoked the words of a professor to explain the story’s genesis and ultimate success: “Don’t forget to frame your emotions as data!” Here’s her admonition that tears can indeed trump big data:

The documentary on YouTube now has nearly 9.4 million views—compared with 7.1 million on the 3-minute song Sobiech initially recorded. While social media played a huge role in this story spreading, traditional media offered even more of a boost in recent days. Yesterday, the Times of India called Sobiech “the heart-warmer of the year.” Katie Couric tearfully interviewed his girlfriend, bandmate and mother, who candidly describes Sobiech’s final moments:

He was at home, Amy (Zach’s girlfriend) had stayed over late that night. Myself and Amy slept in the same room as him. He had a very difficult hour and a half; the cancer had filled his lungs and his lungs had filled with fluid so he essentially suffocated, and that is not an easy way to die, but that was the way he wanted to die. He wanted to be conscious and he was. As hard as those memories are to be there while he suffered so much, we’re so blessed because we were there — we were all there.

The week he died, Zach Sobiech became the first independent artist to take the No. 1 spot on iTunes; it has been downloaded more than 200,000 times (and is currently 67). His album, which includes “Clouds,” is also charting well on Billboard, and is the top folk album.

The Zach Sobiech Osteosarcoma Fund at Children’s Cancer Research Fund has received more than $325,000 from individuals and, soon, proceeds from songs purchases will be added to that total, and Huson reports “myriad fundraiser ideas” rolling in every day, from around the world. She notes, “It’s as if a digital wave lifted that kid right up to the ‘Clouds’ he sang about.”

There is no shortage of popular music inspired by death, but rare is the artist who is the one dying, who invites the world in to join the journey. Our fascination and fanaticism with his song and story might be explained by an eventuality and universality he understood, unfairly and earlier than most people: We’re all going to die. So what are you going to do with the final days of the life you have?