I've read another story on this and they'll use the group to distract the victim while the person who does the assault comes up from behind to suckerpunch the person. If you want to see how hard you can hit someone, do like martial artists and grab some 1" pine boards and some patio bricks to vent your frustration on. Plus, it would be hilarious to see people bust their knuckles because they hit a board with tons of power but improper technique.