Robert Mullen has dedicated his life to helping people with special needs. By day, he works for the largest disability care provider in New Zealand. And in his free time, he continues to help through the power of music.

Mullen teaches people with special needs how to play guitar, but he prefers to be called a "mentor" rather than teacher, he told CBS News. He often posts videos of his lessons, and one student in particular has gone viral.

His name is Alex, and he's a 27-year-old man with Down syndrome and exceptional musical abilities. "[Alex] is a true example of someone who's ability is far greater than their disability," Mullen told CBS News.

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Mullen said he was approached a few months ago about giving Alex guitar lessons. "Within our first two lessons I started to discover he had far more potential and we started exploring with his song writing and then vocal training and any other way to channel his creativity," he said.

Alex's goal was to make a YouTube video, so Mullen started recording their jam sessions at the end of each lesson and posting them on Facebook.

A recent video of the duo performing "Chasing Cars" by Snow Patrol went viral, completely delighting Alex.

"Chasing Cars" remix with this legend. Posted by Robert Mullen Junior on Tuesday, October 30, 2018

As Mullen strummed his guitar, Alex played the harmonica. Then, in the middle of the song, Alex started rapping – wowing viewers with his self-written lyrics.

"I have always been fascinated with the power music has and its ability to be able to unlock hidden treasures within people," said Mullen, who has worked with people with disabilities for 17 years. That's why took break from work for two years to study music. Now, he's able to combine his two passions.

Since the video was posted, Mullen and Alex have been asked to perform the song at two different events. Mullen hopes to keep getting gigs with Alex, and to keep inspiring people with music.

"I'm working with more people with learning disabilities or low self-esteem," the mentor said. "Using music and creativity to help them both express themselves and grow within their personal development."