It's called: The Knockout game.
The rules are simple- You are walking down a sidewalk & ya go to pass a person walking in opposite direstion. Just before ya pass that unsuspecting person, ya haul off and slam your fist into that person's jaw. The object of game is to hit the person hard enough that ya knock them out and ya walk away without a backward glance.
So far, women above the age of 60 are the usual targets, but men & women of all ages are targets.
The people that are hit just crumple to the ground & can recieve further injury by slamming their heads on concrete.
Because of cameras, posted around, several people have been arrested for this game/crime.
I can only hope this crap is stopped before any more folks are injuried.

My question is: WHY??? Are some creeps bored? A right of passage? What?
I'll never understand what goes on in the dark recesses of the mind!