It's very obvious to the rest of us, and if you look further you will find that the big kid has been picked on for years.
It looks like the little bully comes from a family of bullies, as his mother is insisting that the family of the big kid apologize to the bullies family..
The mothers actions are also those of a bully.
She feels humiliated because the video has gone viral and the bullies family is getting all sort of grief now that his victim has stood up for himself.
Someone else posted that the bully’s mother said he deserved what he got.
My only point was based on the video. It comes on with the smaller kid throwing a few punches to little effect for a second or two, followed by the big kid picking him up and slamming him.
Without knowing the back story I could not possibly determine one is a bully, the other the victim. There could have been other punches or whatever before the video started.