YOU SAID:

i went to the store to get some bread but came back with a cat. i don't know how it happened

INTO JAPANESE

パンを買いに店に行きましたが、猫と一緒に戻ってきました。どうして起こったのかわかりません

BACK INTO ENGLISH

I went to the store to buy bread but came back with the cat. I don't know why it happened

INTO JAPANESE

パンを買いに店に行きましたが、猫と一緒に戻ってきました。なぜそれが起こったのか分かりません

BACK INTO ENGLISH

I went to the store to buy bread but came back with the cat. I don't know why it happened