This is an interesting case. I'm all for non violence, but if i was in the same situation I can't say I wouldn't have done the same. As far as the fathers guilt, well it hard to say. While I don't think it was right for him to kill another person I can only imagine the blind rage that must have over taken him upon seeing what he saw. Its possible that he may not have been aware of just how hard he was hitting the victim.
"At least Deathcore was heavy as shit when done right, this new stuff sounds like if meshuggah and taking back sunday had a homosexual he/she creature when bred together." -- Some dude on youtube