By Rachael Smith, Alumna of Radford University

Video sensation 18-year-old Zach Sobiech passed away on Monday of osteosarcoma. On Tuesday, my Facebook was filled with friends posting a video over and over again and many other liking it and commenting on it.

I just had to know what this was, but I had no idea what I was getting into. I thought I was about to watch a three-minute video about a cool kid. Twenty minutes later, I’m crying like a baby on my bed wishing I could have just met Sobiech.

There are plenty of sad cases where young people tragically die every day, but what made him so famous? Last June, after he found out he had six months to a year to live, Sobiech sang and recorded a farewell song to his loved ones named “Clouds.” By December, it was a YouTube hit and No. 1 on iTunes. This caught the attention of film director Justin Baldoni, who in turn, created a documentary on the Sobiech family and the teen's final days. The short film is called “My Last Days: Meet Zach Sobiech.”

But what makes Sobiech so special? He is the ultimate optimist. It’s crazy to watch throughout this entire video how he continues to live his life although he knows it hardly has any of it left.

Since the age of 14, he has learned to live with osteosarcoma and somehow still be an outstanding student, friend, boyfriend and family member.

"My closure is being able to get my feelings into these songs so they can have something to remember me by or lean on when I'm gone,” Sobiech says in the video. “I want to be remembered as a kid who went down fighting and didn't really lose."

If you haven’t already, click here (or below) to watch the documentary. Make sure to watch the whole thing, no matter how much you tear up.