YOU SAID:

I am going to kill everyone in this room and then myself

INTO JAPANESE

私はこの部屋の誰もを殺すつもりです。

BACK INTO ENGLISH

I am going to kill everyone in this room.

INTO JAPANESE

私はこの部屋の皆を殺すつもりです。

BACK INTO ENGLISH

I am going to kill everyone in this room.