YOU SAID:

I dreamed of killing someone, so i did

INTO JAPANESE

私は誰かを殺すことを夢見ていたので、やった

BACK INTO ENGLISH

I did it because I dreamed of killing someone

INTO JAPANESE

私は誰かを殺すことを夢見ていたのでそれをしました

BACK INTO ENGLISH

I did it because I dreamed of killing someone