How did kevin from the jabbawockeez do the punch illusion at the battle for the vma's?

If you watch the video carefully, when he does the punch through his shirt, it still looks like both of his hands are in the sleeves while he does the punch. Did someone behind him do it or was it himself? Is so how did he do it?|||Someone behind him to his left and our right stuck their arm in his coat/jacket


that's why he leaned to his left, to hide the other Jabbawockeez arm