WATERTOWN, Mass.- An employee at a grocery store stopped customers in their tracks when he began singing classical Christmas carols on Friday.

23-year-old Gilly Assuncao, from Brazil, has always been passionate about music. When he stepped in to help the musical act the store hired with their sound check, shoppers were stunned.

"I heard this incredible operatic sound coming from the greenhouse." an employee said. "I kept walking closer and I thought it was definitely some kind of tape recording."

Assuncao dreams of attending Berklee College of Music in Boston, but says he can't afford it. 

The video is quickly going viral and Assuncao says he's completely shocked by all of the attention. "I honestly was not expecting that at all," he said. "I just thought it was going to be a cool performance here in the store."

Check out the video to hear his incredible voice.