YOU SAID:

he comes at me with knife, saying 'WHY SO SERIOUS'

INTO JAPANESE

彼はナイフで私にやって来て、「どうしてそんなに深刻だ」と言った。

BACK INTO ENGLISH

He came to me with a knife and said, "Why are you so serious?"

INTO JAPANESE

彼はナイフで私のところに来て、「どうしてそんなに本気なの？」と言った。

BACK INTO ENGLISH

He came to me with a knife and said, "Why are you so serious?"