Bieber, back in the day!

In August 2007, Justin Bieber was just an unknown, baby-faced young singer with a dream and a guitar.

In new pics acquired exclusively by UsMagazine.com, a pre-fame Bieber, then a wee 13 years old, played his guitar and sang on the concrete steps of the Avon Theatre in his hometown of Stratford, Ontario.

Photographer I. Shuter, who snapped the pics, tells Us he noticed "this cute kid" performing just past 9 a.m. on Aug. 20 — with passersby throwing dollar bills and loose change into his guitar case.

Sadly, Bieber's impromptu show came to an abrupt end. "The manager of the theater came and chased the kid away!" Shuter tells Us.

The "Baby, Baby" singer has said he earned $3,000 "busking" outside the Avon Theatre; a YouTube clip of him singing at a talent show earlier that same year eventually launched his stardom.

When his future manager Scooter Braun discovered the clip, Bieber landed the record deal that changed his life.

"He was the most talented kid I'd ever met!" Braun says.

Read much more about Justin's rise to fame in Justin Bieber: My Private World from the Editors of Us Weekly — in bookstores and online now!