YOU SAID:

I killed a baby with a rock and then ate it for dinner

INTO JAPANESE

岩で赤ちゃんを殺して夕食に食べました

BACK INTO ENGLISH

I killed the baby on the rock and ate it for dinner

INTO JAPANESE

私は岩の上で赤ちゃんを殺し、夕食にそれを食べました

BACK INTO ENGLISH

I killed the baby on the rock and ate it for dinner