Justin Bieber Tantalizes Crowd with Shirtless Skateboarding Exhibition

A crowd of Justin Bieber fans was thrilled to see their hero skateboarding outside his recording studio in Miami last night -- then he took off his shirt and they went BALLISTIC.

Bieber was at the Hit Factory and a crowd of about 60 fans gathered outside. According to one witness, the group waited about five hours for a glimpse of the Biebs, when he finally obliged and came out to skateboard for a few minutes.

The most disturbing part ... after he took off his shirt and the screaming subsided, one girl BEGGED for Justin to give her his shirt, promising, "Please, we'll share it!"