The reason that he wanted to kill the little boy was

that he didn't want people to find out that is his Illegitimate son. Remember that Mrs boss told the bad guy that;" I will tell your wife he is your son"?

On the end of the party, the rich guy, the father of the bad guy told his son:"I will disinherited you, you fool around with those savages..." That was the reason the bad guy pushed his father into the pond, and let crocodile ate his dad.