See link below.
A bunch of teens likely playing 'knockout'...quite brutal actually.
(Drop down to the end of the article for the video.)
The teacher clearly did the wrong thing, but what would you do if you found yourself in the teacher's position.
Turn around? Move over further and keep walking? Stop and wait for them to pass?
And each of those actions may also be viewed as provocative.
Jim Addlespurger: CAPA teacher attacked by teens in alley | Mail Online