YOU SAID:

Peter is dead and we don't know why

INTO JAPANESE

ピーターは死んだ、何故だか分からない

BACK INTO ENGLISH

I don't know Peter is dead, why?

INTO JAPANESE

ピーターがなぜ死んでいる、私は知らないか。

BACK INTO ENGLISH

Why Peter is dead, I don't know.

INTO JAPANESE

なぜピーターは死んでいる、私は知らないです。

BACK INTO ENGLISH

Peter is dead, I don't know why.

INTO JAPANESE

ピーターは死んでいる、私は理由を知らない。

BACK INTO ENGLISH

Peter is dead, I don't know why.