This blind teen went viral for singing the national anthem. He hopes his voice will bring joy to others.

Sawyer McCarthy communicates best through music. The 13-year-old from South Carolina is blind. But his other senses — like his voice — are strong. 

In April, he sang the national anthem at a Columbia Fireflies game, reaching millions of viewers — not only in America but around the world. 

"I remember asking him one day, 'How many people do you think saw your video?'," his mom, Brianna McCarthy, told CBS News, turning to her son. '"You answered me and you said, 'Four.' I said, 'Yeah, try like four million.'" 

With no singing lessons until very recently, Sawyer McCarthy has managed this far with nothing but his natural talent. His mother would share videos of him singing on Facebook. 

"We realized that the way Sawyer communicates best is through music," she said. "He's always, always had a knack for hearing noises that even we don't notice."

He recalled what his vocal coach told him during one of their first lessons when the coach used a really cool word.

"I don't hear a lot of people say this, but he says my voice is very impeccable," he told CBS News. "And I'd never heard anyone say that to me before." 

Sawyer was born blind but his mother didn't know until he was 3 months old. 

"I was taking Sawyer for a stroll outside," Brianna said. "And I noticed that we were in direct sunlight, but he wasn't squinting."

Doctors later diagnosed Sawyer with septo-optic dysplasia and optic nerve hypoplasia, a genetic condition affecting one in 10,000 children, according to the Cleveland Clinic. 

Brianna and her husband Patrick hope their son, the oldest of their six kids, will be able to live as independently as possible. 

"He reads Braille. He uses a cane. But there are also some developmental delays," she said. "The older he gets, we're just not sure what the future looks like." 

Even at such a young age, Sawyer has big ambitions. He hopes to perform on "America's Got Talent" — despite being nervous about what Simon Cowell might say, his mother said. 

But no matter what happens, one thing's for certain: Singing is in his past, present and future. 

"How do you think it makes people feel when they hear you sing," Brianna asked her son. 

"Joyful," he responded, to which she happily agreed.