It will sadly get worse. The video is just one that has been posted but similar goes on up and down the country in small shops and businesses daily. Youths will mob a place, overwhelm the staff and grab what they are going for, mainly drink and cigarettes. Some eventually get caught, the majority don't.
I was on the tram a few weeks ago and it pulled into Sale station. About thirty teenagers, all together, piled on for a few stops. Luckily they were just obnoxious, shouting, swearing, swinging from overhead straps but it was an extremely unpleasant experience. If they had started attacking and/or robbing people we'd have been fucked. The oldest was probably sixteen but the weight of sheer numbers would have overpowered anyone standing up to them and that's before you consider the possibility of weapons. I've been in hotspots all over the world and I'm no mug but my heart rate was going. For anyone less worldly wise it must have been terrifying.