Justin Bieber's Bodyguard Takes Down Photographer

TMZ obtained video of the altercation between the Bieb's protector and the paparazzo -- not one of our guys -- and when the clip begins the bodyguard already has the pap in a headlock.

After several moments of grappling, the photog breaks free to square off with the bodyguard -- BIG mistake ... 'cause that's when the bodyguard uncorks a straight right to the photog's face.

As TMZ first reported, according to Bieber's camp the altercation began when the pap jumped in front of Bieb's SUV and refused to stop snapping pics.

The pap was arrested and booked for assault with a deadly weapon ... a felony.