VIDEO OF PENNSYLVANIA TEACHER KNOCKED OUT UNSUSPECTINGLY BY TEENAGERS

Unsuspecting: Jim Addlespurger was walking down an alley near his school in downtown Pittsburgh, Pennsylvania, when he was attacked

A chilling surveillance video  shows the moment a respected high school teacher was knocked out cold by an unprovoked sucker punch after passing a group of teens in an alley.

Jim Addlespurger, who was walking near his school in Pittsburgh, Pennsylvania, is seen crumpling to the ground and smashing his head on a curb.

The six teens laugh and celebrate the horrifying attack as they coolly walk away from Mr Addlespurger, 50.

Police do not believe the attackers attend Mr Addlespurger's school. Class was still in session at the time of the attack.

Mr Addlespurger was taken to the hospital, where he was treated for cuts and bruises. He is currently at home healing from his injuries, WTAE-TV reports.    

Police have released video of the brazen daylight assault on Thursday afternoon, hoping the public can identity the teens.

Mr Addlespurger was just a few blocks from the Creating and Performing Arts School in downtown Pittsburgh, where he teaches 10th and 12th grade English. 

Respected: Mr Addlespurger teaches 10th and 12th grade English at Creative and Performing Arts School, which is near the alley where he was assaulted.

The video shows him walking through an alley carrying his briefcase as the six teens walk past in the other direction.

Suddenly, a student steps into the teacher's path and punches him in the face. 

The boy's friends seem gleeful, but not surprised by the assault.

Several bystanders are seen helping Mr Addlespurger as he struggles to his feet. 

Several witnesses saw what happened and numerous surveillance cameras captured the teens on tape.