YOU SAID:

I'm going to kill whoever did this with a knife

INTO JAPANESE

私はナイフでこれをした人を殺すつもりだ

BACK INTO ENGLISH

I'm going to kill someone who did this with a knife

INTO JAPANESE

ナイフでこれをした人を殺すつもりだ

BACK INTO ENGLISH

I'm going to kill someone who did this with a knife.

INTO JAPANESE

私はナイフでこれをした人を殺すつもりです。

BACK INTO ENGLISH

I am going to kill someone who did this with a knife.

INTO JAPANESE

私はナイフでこれをした人を殺すつもりです。

BACK INTO ENGLISH

I am going to kill someone who did this with a knife.