Regardless of why or how this happened, this is a brutal fucking video. Tough to watch, really.
According to a commenter on Live Leak, below is the translation of the conversation this father and son had prior to the face-kick from hell:
Son: go ahead hit me , hit me
Father: Suck my dick you piece of trash
Son: go ahead hit me if you think your tough
Father: Poooow, i will, you fuckin shit.
After the hit father was like "don't have to ask me twice."
Of course, that translation could be completely inaccurate -- I have no clue, other languages sound like animal noises to me. That said, if you happen to speak Russian (or whatever this is), feel free to send in a alternate attempt.