This is a vicious and slick use of the knee, head butt, and U-Punch. I catch people with it all the time. The followup ground kick is extremely violent and usually enough to KO even the biggest meanest BG who might mess with you. Like I said many times before: capoeira is a devastating fighting martial art. Let's never forge that and practice it accordingly, or we will LOSE our beloved capoeira as it becomes some shallow folk dance and then withers away into an obscure, tragic death.