What Should I Do To My Dad That Slapped My Mom And I?

A member of a popular online forum this morning said he was slapped by his father for confronting him on why he slapped his mother. According to him, before he could finish, the father gave him a slap. Read what he said:
" It happened this morning oh, was bathing and prepping for work when i heard my dad at the top of his voice, before i knew it i heard mumsy crying, he had slapped her. Am in the same house( Haven't been able to move out yet) and i couldn't just bear my mum crying so i went to my dad to tell him what he did was not right. He is almost 60 and so is his wife, at that age you slap your wife i was trying to use the voice of reason as i was angry but kept my calm (Who wouldn't be angry seeing his/her mum cry?) before i could finish explaining and appealing to him i received from his left hand of righteousness a resounding slap... it got me confused as i didn't know what i did to deserve such. I didn't say anything harsh nor abusive. Am angry but didn't wanna return that slap nor say words I'll regret. I told him I'm moving out and he just lost a son, he replied that i wont be missed. I wanna do something he'll never forget, before i leave, please i need advice as it dented my personality even amongst my younger siblings and neighbors. I really am confused on what to do before moving out. Am so pissed now
pls sincere advice. thanks

He is now asking people what he should do to his father! How do you see it? Is he acting normally or not? Well, as far as i am concerned, a child must never raise his hands on his parents. Lets hear what you think of this story...